4.2.3 Empiricism


By the end of this section you will discover:

  • How 18th century empiricism sought knowledge not in innate ideas but in the observation of the universe.
  • How John Locke established the foundations of empiricism by seeing knowledge as the acquisition of simple ideas of sensation which eventually combined into complex ideas.
  • How the philosophers George Berkeley and David Hume advanced Locke’s basic principles but modified his conclusions.
  • Strengths and weaknesses of the empiricist approach to knowledge.


Nothing ever becomes real until it is experienced…. John Keats


Whereas the Rationalists tended to distrust the evidence of the senses, the British Empiricists of the century after Descartes and Leibniz believed the senses were the foundation of knowledge. It’s the mind and its abstractions, they argued, that confuse us. The 18th century in Britain saw a rush of scholars fascinated by the science of Isaac Newton and the new empiricist philosophy.

Locke, Berkeley, & Empiricism: Crash Course Philosophy #6

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Empiricism in Ancient Greece: Aristotle

We noted in our discussion of early Greek philosophy that there were many famous philosophers before Socrates (the Pre-Socratics) who were fascinated by the nature of reality and held varying ideas about the natural world and its origins.  Their scientific explorations were of much interest to Plato’s most famous student, Aristotle.

Aristotle was born in Stagira in Macedonia. His father was a court physician to King Amyntas, the founder of the Macedonian power and the father of King Philip. Little is known about the early years of Aristotle except that his father and mother died, leaving him in the guardianship of Proxenus of Atarneus. It can scarcely be doubted that he was destined by his family to be a physician and that the empirical works of Hippocrates and Democritus were the first elements of his early education. Aristotle grew up in this atmosphere of medicine in Macedonia, which explains his respect for the results of experience and his accuracy in detail.

Bust of Aristotle. Marble, Roman copy after a Greek bronze original by Lysippos from 330 BC; the alabaster mantle is a modern addition.
Aristotle (384–322 BC)

At age 18 he was sent to Plato’s Academy, where he studied and worked for nearly twenty years. He was not merely a pupil in the school, but his brilliance won him immediately a prominent position there. He became a teacher, an attractive writer, and a champion of the literary spirit of the school. Even while he was a member of the Academy, he became a famous man. It is difficult to say just how much influence the Academy had upon the casting of his thought. His scientific inclinations were formed before he went to the Academy; he got his immense scientific erudition in Asia Minor and in Stagira later, after he left the Academy. Probably the spirit of the Platonic school turned his attention to ethical and metaphysical theories, and probably it was due to his stay in the Academy that he became interested in rhetorical and purely cultural studies. At the same time, his own influence must have been very great in forming the policy of the Academy, and he was probably responsible for turning its attention to scientific matters.

The sources from which Aristotle drew the material of his philosophical science were, therefore (1) his inherited taste for medicine and the empirical science of the pre-Socratics; and (2) the influence of the Academy on ethical, metaphysical, and cultural subjects. Both these factors appear throughout the philosophical development of Aristotle. On the other hand, it must not be forgotten that probably Aristotle’s influence upon the Academy was as great as that of the Academy upon him. … Aristotle held his master in great esteem, as he himself testifies in his Ethics. Aristotle was an independent and original mind, and probably even while in the Academy he would point out defects in Plato’s thought when his aged teacher would lead his theories upon mistaken lines. Plato said that his pupil Xenocrates needed the spur, while Aristotle needed the bridle. Aristotle was called the brain of the Academy.

In 343 B.C.E. he obeyed the summons of King Philip to come to Pella and become the tutor of Alexander. He acted in this capacity for four years and seems to have been more fortunate than Plato as an instructor of a king. His influence upon Alexander was very great. Without losing himself in the impracticable, Aristotle seems to have impressed high philosophical ideals upon the noble spirit of his kingly ward. Alexander says of Aristotle, “To my father, I owe my life, to Aristotle the knowledge of how to live worthily.” The ideals of statesmanship, the wide purposes in political control, the greatness of the aims of the young conqueror, as well as his self-control, his aversion to meanness and petty things, and his sublime moderation were due in part to the teachings of Aristotle. Never was there a more fortunate conjunction of two great minds than here.

When Alexander entered upon his campaigns in Asia, and Aristotle felt himself free from his immediate duty to him, he went to Athens and founded the Lyceum. This school very soon arose above the Academy and became the model of later societies of scholars of antiquity. Its greatness partook of the greatness of Aristotle—in the universality of its interests, in the orderliness of its administration, and in methodical cooperation. For twelve years he was the executive, teacher, administrator, and inspiration of this school—developing his philosophy, accumulating materials, and instructing his pupils. The enormous product of the school could not have been the work of one pair of hands. Nevertheless, the writings, the immense collections, the ethical and political treatises, show a unity that speaks of one mastermind that had them under direction. When the Athenians began to rise against the Macedonian rule, Aristotle’s position in Athens as a friend of Alexander became unsafe. He fled to Chalcis, excusing himself, so the tradition goes, because he wished to spare the Athenians a second crime against philosophy. He died in Chalcis the next year (322 B. C.). (Cushman, Beginner’s History of Philosophy, Vol 1, Ch. VIII, Aristotle, Project Gutenberg)

You will recall that Plato seriously distrusted the data of the senses and equated the sights, sounds, tastes, touches, and smells of ordinary experience with mere shadows on the wall of a cave.   Instead, Plato stressed we must move beyond the senses and enter the realm of the mind (above “the Divided Line”) and there recognize the “forms” or ideas in their purest existence. The things of ordinary experience could not be real, for Plato, for they all dissipated and ceased to exist. Only their forms, the concepts that helped us perceive them, can be said to be unchanging, non-dying, and therefore real.

Ponder if you will….

Who are you? Are you the parts of yourself that can be weighed and measured and scientifically cataloged? Or are you something in addition to those physical properties? When your body dies, will there still be a “you” somehow? Or do you agree with Aristotle, that the individual dissipates at death?

Aristotle disagreed, to a point, with his great teacher. He accepted the notion of “the forms” as needed for perception, but these forms did not exist in some transcendent place apart from the sensory world, but in fact, are only known by experiencing the particular things of the world. The way to understand the form “giraffe” is not to sit and meditate on definitions and concepts but to actively go out and observe the many giraffes in the natural world. Through such observations, we can recognize what Aristotle called the “formal cause” of a particular, concrete giraffe, as that energy that makes him a giraffe, in combination with other causal energies, including the material (the stuff of which the giraffe is made), effective (what came before this particular giraffe to make it come into existence, i.e. its parents) and final (is the purpose or destiny of the giraffe). These four causes all contribute to the particular giraffe we are observing.

However, that giraffe will someday go out of existence. When it does, says Aristotle, its causes will also die. It will no longer have matter, effect, or destiny. Nor will it have form. Here Aristotle rejects Plato’s belief that for something to be real it must be eternal, non-dying. Quite the contrary, said Aristotle. Reality, the form of a thing, is temporary and exists only so long as the particular thing exists.

Note too, that we are not born with a set of innate ideas which we “remember” as we grow older as Plato believed. For Aristotle, the mind does not contain the forms but perceives them in the patterns and categories of the particular things of nature. We are not born with the concept of “giraffe” in our minds, but by observing multiple things like giraffes we can discern the general form which exists in the things themselves, not in the mind.

This view sets the ground for the tradition of empiricism, the epistemological position that states that knowledge comes from the observation and experience of the world around us, not from any innate wisdom. Empiricism in Early Modern Europe: Locke, Berkeley, and Hume

If the 17th century in Europe was the age of the great rationalists, the 18th century saw the emergence of the empirical tradition, especially in Great Britain.

Portrait of Isaac Newton at age 46 by Godfrey Kneller, 1689
Isaac Newton (1642-1727)

This was the century in which the great mathematician and scientist Isaac Newton published his groundbreaking Philosophieae Naturalis Principia Matematica, which articulated a mathematical and mechanical understanding of the universe. The mechanical philosophy was a philosophy of nature, popular in the seventeenth century, that sought to explain all natural phenomena in terms of matter and motion. In Newton’s mechanical universe there was no room for non-physical realities like souls and gods. All existence is material, devoid of the spiritual, and deterministic, with events leading inevitably and predictably to new events in a causal sequence.

John Locke

Portrait of Locke in 1697 by Godfrey Kneller
John Locke (1632 –1704)


A close friend and scientific collaborator with Newton was the philosopher John Locke. Locke (1632 –1704) … develops his empiricist epistemology in his Essay Concerning Human Understanding. Locke’s approach is to examine the origins of the contents of the mind. Early in this work, he argues against innate ideas. Locke suggests that the mind starts off as a tablula rasa, a blank slate [an idea Locke borrowed from Aristotle.]

All of our ideas have their origin in experience.   Simple ideas, say of solidity and figure, are acquired through the senses, and from these, we form complex ideas, say the idea of a dog, through the capacities of the understanding. The details of this account raise a number of challenging questions. We might think of Locke as launching a research program for developing an empiricist account of the mind rather than spelling out a fully developed view.


Ponder if you will….

an image of a banana
Consider how Locke would explain your perception of, say, a banana. When you experience the banana, at first the mind takes in simple sense data which Locke would call simple ideas of sensation. These would include the smoothness of the skin, the yellow and green of its surface, its smell, and its taste. All of these simple ideas then come to be knowledge by a three-fold mental process of compounding (piecing all these simple ideas together), relating (comparing the construct to similar perceptions past or present), and abstracting (to general notions like fruit, edible, etc.).
This is how Locke claimed we come to knowledge from sense experience alone.

Locke thinks that some of the impressions we get from sense experience are genuinely similar to how things are objectively in the world. Our sense experience of the shape of things, for instance, reflects the ways things really are according to Locke. Locke refers to the qualities where there is a resemblance between our experience and the way things are as primary qualities. Shape, motion or rest, and number are a few of the primary qualities.

Ponder if you will….

Think of a dog.

What ideas about a dog would Locke say are simple? What ideas are complex?

What qualities of a dog would Locke say are primary qualities? Which qualities are secondary qualities?

Other aspects of our sense experience don’t exist within the objects. The taste of an apple, for instance, is not really in the apple. What is in the apple is just a power to produce the experience of a certain flavor. But we have no grounds for thinking that this power as it exists in the apple resembles in any way the sense experience we have of its taste. Locke calls qualities where our sense experience doesn’t resemble the qualities that give rise to our experience secondary qualities. Our knowledge of the external world, then, is based entirely on our experience of the primary qualities. Empiricism, as we will see in the case of later empiricists, especially Hume, tends to place sharp limits on what is knowable.

Representative Realism: The belief that at least some of the information in our perceptions gives us true information about the objects outside of the mind we are perceiving. For Locke, the Primary Qualities of an object could be so trusted.

While all experience depends on having simple ideas taken in through sense experience, Locke does not take experience to be limited to these. We also experience the operations of the mind in building up complex ideas out of simple ideas. Once you have some simple ideas through sense experience, you also have an experience of yourself and of your mental operations on those simple ideas. So given simple ideas through experience, the operations of the mind become a source for further ideas. Locke thinks knowledge of the self, God, mathematics, and ethics can be derived from this additional internal source of experience. Hume, as we shall see, is not so optimistic. (Payne, Ch. 5)

Excerpts from Locke’s Essay Concerning Human Understanding
In the passage that follows, Locke suggests that knowledge arises from two processes or sources.  How does he begin to refute the Rationalist’s contention we are born with innate ideas?


Every man being conscious to himself that he thinks; and that which his mind is applied about whilst thinking being the “ideas” that are there, it is past doubt that men have in their minds several ideas, —such as are those expressed by the words whiteness, hardness, sweetness, thinking, motion, man, elephant, army, drunkenness, and others: it is in the first place then to be inquired, how he comes by them?

I know it is a received doctrine, that men have native ideas, and original characters, stamped upon their minds in their very first being. This opinion I have at large examined already; and I suppose what I have said in the foregoing Book will be much more easily admitted, when I have shown whence the understanding may get all the ideas it has; and by what ways and degrees they may come into the mind; —for which I shall appeal to every one’s own observation and experience.

To what does Locke famously compare the mind prior to sensation?

Let us then suppose the mind to be, as we say, “white paper,” [tabula rasa] void of all characters, without any ideas: —How comes it to be furnished? Whence comes it by that vast store which the busy and boundless fancy of man has painted on it with an almost endless variety? Whence has it all the materials of reason and knowledge? To this I answer, in one word, from experience. In that all our knowledge is founded; and from that it ultimately derives itself. Our observation employed either, about external sensible objects, or about the internal operations of our minds perceived and reflected on by ourselves, is that which supplies our understandings with all the materials of thinking. These two are the fountains of knowledge, from whence all the ideas we have, or can naturally have, do spring.

What for Locke are the two sources for the two kinds of ideas we have in our minds?

First, our Senses, conversant about particular sensible objects, do convey into the mind several distinct perceptions of things, according to those various ways wherein those objects do affect them. And thus, we come by those ideas we have of yellow, white, heat, cold, soft, hard, bitter, sweet, and all those which we call sensible qualities, which when I say the senses convey into the mind, I mean, they from external objects convey into the mind what produces there those perceptions. This great source of most of the ideas we have, depending wholly upon our senses, and derived by them to the understanding, I call “sensation.”

Secondly, the other fountain from which experience furnishes the understanding with ideas is, —the perception of the operations of our own mind within us, as it is employed about the ideas it has got; —which operations, when the soul comes to reflect on and consider, do furnish the understanding with another set of ideas, which could not be had from things without. And such are perception, thinking, doubting, believing, reasoning, knowing, willing, and all the different actions of our own minds; —which we, being conscious of, and observing in ourselves, do from these receive into our understandings as distinct ideas as we do from bodies affecting our senses. This source of ideas every man has wholly in himself; and though it be not sense, as having nothing to do with external objects, yet it is very like it, and might properly enough be called “internal sense.” But as I call the other Sensation, so I call this “reflection,” the ideas it affords being such only as the mind gets by reflecting on its own operations within itself. By reflection then, in the following part of this discourse, I would be understood to mean, that notice which the mind takes of its own operations, and the manner of them, by reason whereof there come to be ideas of these operations in the understanding. These two, I say, viz. external material things, as the objects of “sensation,” and the operations of our own minds within, as the objects of “reflection,” are to me the only originals from whence all our ideas take their beginnings. The term “operations” here I use in a large sense, as comprehending not barely the actions of the mind about its ideas, but some sort of passions arising sometimes from them, such as is the satisfaction or uneasiness arising from any thought.

The understanding seems to me not to have the least glimmering of any ideas which it doth not receive from one of these two. External Objects furnish the mind with the ideas of sensible qualities, which are all those different perceptions they produce in us; and the mind furnishes the understanding with ideas of its own operations….   (Gutenberg, Locke, Essay Concerning Human Und)

Portrait of Berkeley by John Smybert, 1727
George Berkeley (1685-1753)

George Berkeley

George Berkeley (1685-1753) was an empiricist philosopher and also a Bishop in the Anglican Irish Church. Although he admired the work of Newton and Locke, he was distressed by the materialism implied by their thought. If all that exists are those parts of the universe available to the senses, what becomes of spiritual realities like the mind, the soul, and God?

Berkeley attacks Locke’s distinction between primary and secondary qualities and argues that all of our sense impressions are mere appearances and that we have no grounds for thinking that any of them bear any resemblance to the way things are. Since we lack any empirical experience of the underlying substances [i.e., the things in themselves outside of our experience] … we have no empirical reason to suppose underlying substances even exist. All we have access to are our sense impressions, and these are mental things, ideas. So, all we can claim knowledge of are our ideas beginning with our sense impressions, the most basic ideas. (Payne, Ch. 5)

Berkeley believed that Locke’s conviction that we can know information about objects (at least their primary qualities) outside of the mind was impossible. For even the primary qualities are mental events for the perceiver. If someone says that a banana is 7.5 inches in length, that measurement, that primary quality, is still true only of the percept as known in the mind. Locke was wrong to make the representative realism leap to saying that those measurements also exist outside the mind. In fact, Berkeley argued that nothing existed outside of the mind. The world we perceive is entirely a mental world, composed of thought.

Taking it to the Streets….

Berkeley’s idealism argues that we are unable to say anything about the existence of what might be outside of our minds. Is he right?
Ask several friends to suggest things that that they “know” exist that do not appear to their minds.
If they can suggest some things, ask them “where” it is in themselves they “know” them.
If you convince them that what they know they know only in their minds, ask them how they could ever be sure that what is in their minds is also in the world outside their minds.

But can we say such a world is real? Berkeley insisted very much that we can. His idealism—the philosophy which states that all reality is mental and not physical in nature—came from his insistence that esse est percipi, to “be” is to “be perceived” by a mind. Here Berkeley is radically upending our notion of what it means to exist. Existence is caused by perception. Perceptions are mental events, as are the things being perceived. There is no way to ever get “outside” of the mind. All that we know, we know inside the mind.

Strange as this idea may appear to us, modern quantum mechanics suggests something quite similar. The double slit experiment has shown quite compellingly that light exists only when perceived. The experiment showed that when not being “measured” by an “observer,” light particles do not exist as particles, but merely as waves of potential. The act of deliberately observing them by measurement “collapses” that wave of potential particles into a single particle, causing it to “exist.

To see a more contemporary expression of the notion that a thing exists only when it is perceived, watch this good explanation of Quantum Mechanics, paying particular attention to the “double slit experiment” and its implications:

Film: NOVA The Fabric of The Cosmos: Quantum Leap

However, Berkeley is left with a problem. If things exist only when perceived, does that mean things stop existing if we walk out of the room or fall asleep? And how can we know that we share a common reality? Is it not possible that I am perceiving things quite differently than my friends? Is existence entirely subjective?

In response to these concerns, Berkeley reminds us that ours is not the only mind! He posits the reality of a Great Mind, the mind of God. He argues that we can infer God’s existence from the fact that we encounter ideas we do not will ourselves to have. Since only minds and ideas exist, and only minds cause ideas, then involuntary ideas must be caused by some other mind, and most of the time this mind is God’s.

The existence of a Great Mind lends objectivity and reality to the contents of our minds. We can be sure we are seeing the world the same way as our friends because the mental realities of ideal objects are guaranteed by the mind of God. God holds all things in a real, though not physical, objectivity.

Excerpts from Berkeley’s The Principles Of Human Knowledge

In the following passage from Berkeley’s Principles, consider:

To what extent does Berkeley agree with Locke’s understanding of how we perceive?

1. It is evident to anyone who takes a survey of the objects of human knowledge, that they are either ideas actually imprinted on the senses; or else such as are perceived by attending to the passions and operations of the mind; or lastly, ideas formed by help of memory and imagination–either compounding, dividing, or barely representing those originally perceived in the aforesaid ways. By sight I have the ideas of light and colors, with their several degrees and variations. By touch I perceive hard and soft, heat and cold, motion and resistance, and of all these more and less either as to quantity or degree. Smelling furnishes me with odors; the palate with tastes; and hearing conveys sounds to the mind in all their variety of tone and composition. And as several of these are observed to accompany each other, they come to be marked by one name, and so to be reputed as one thing. Thus, for example a certain color, taste, smell, figure and consistency having been observed to go together, are accounted one distinct thing, signified by the name “apple.” Other collections of ideas constitute a stone, a tree, a book, and the like sensible things—which as they are pleasing or disagreeable excite the passions of love, hatred, joy, grief, and so forth.

Where does Berkeley differ from Locke?

2. But, besides all that endless variety of ideas or objects of knowledge, there is likewise something which knows or perceives them, and exercises diverse operations, as willing, imagining, remembering, about them. This perceiving, active being is what I call “Mind,” “Spirit,” “Soul” or “Myself.” By which words I do not denote any one of my ideas, but a thing entirely distinct from them, wherein they exist, or which is the same thing, whereby they are perceived–for the existence of an idea consists in being perceived [esse est percipi].

How does Berkeley explain how his desk exists even when he is not experiencing it?

3. That neither our thoughts, nor passions, nor ideas formed by the imagination, exist “outside of” the mind, is what everyone will agree. And it seems no less evident that the various sensations or ideas imprinted on the sense, however blended or combined together (that is, whatever objects they compose), cannot exist otherwise than “inside” a mind perceiving them. I think an intuitive knowledge may be obtained of this by anyone that shall attend to what is meant by the term “exist,” when applied to sensible things. The table I write on I say exists, that is, I see and feel it; and if I were out of my study, I should say it existed—meaning thereby that if I was in my study I might perceive it, or that “some other Spirit” actually does perceive it. It had an odor, that is, it was smelt; there was a sound, that is, it was heard; a color or figure, and it was perceived by sight or touch. This is all that I can understand by these and the like expressions. For as to what is said of the absolute existence of unthinking things without any relation to their being perceived, that seems perfectly unintelligible. Their “esse” is “percipi” [they exist because they are perceived], nor is it possible they should have any existence out of the minds or thinking things which perceive them. (Berkeley, A Treatise Concerning the Principles of Human Knowledge, Gutenberg)

David Hume

David Hume (1711 – 1776) was a Scottish Enlightenment philosopher, historian, economist, librarian, and essayist, who is best known today for his highly influential system of philosophical empiricism, skepticism, and naturalism. Beginning with A Treatise of Human Nature (1739–40), Hume strove to create a naturalistic science of man that examined the psychological basis of human nature. Hume argued against the existence of innate ideas, positing that all human knowledge derives solely from experience.

Hume was by far the most radical of the Empiricists. He refused to discuss anything that did not appear to the mind. Moreover, he agreed with Berkeley that it is impossible to escape the mind to some external reality. But he took Berkeley one step further and said that because we cannot perceive things like minds or Great Minds, we cannot say those exist either! Instead, we must remain skeptical about all that is appearing to the mind. None of it can be known with certainty to exist.

In the following section from Russel Payne, consider,

What terms did Hume use to discuss the ideas that appear in the mind?

A portrait of David Hume by Allan Ramsay, 1766
David Hume (1711 – 1776)


Of the philosophers discussed here, Hume has probably had the greatest influence on contemporary analytic philosophy. The twentieth century begins with a movement known as Logical Positivism that tests the limits of Empiricism. The Empiricism of the Logical Positivists is heavily indebted to Hume.

Hume’s empiricist epistemology is grounded in his philosophy of mind. Hume starts by asking what we have in the mind and where these things come from. He divides our mental representations into two categories, the relatively vivid impressions, which include sensations and feelings, and the less vivid ideas which include memories and ideas produced by the imagination.


How did ideas differ from impressions? Which was more valuable for knowledge?

What distinguishes impressions from ideas in our experience is just their vividness. The picture of the mind Hume offers is one where all of our beliefs and representations are cooked up out of basic ingredients provided by experience. Our experience gives us only impressions through sense experience and internal impressions like feelings. From this, we generate less vivid ideas. Memories are merely faint copies of impressions. Through imagination, we can generate further ideas by recombining elements of ideas we already have. So through impressions, we get the idea of a lizard and the idea of a bird. We can then generate the idea of a dragon by imaginatively combining elements of each. In cooking up new ideas from old ideas, the imagination is guided by associating relations like resemblance, contiguity (next-to-ness), and cause and effect. So, for example, an impression of a grapefruit might lead me to think of an orange due to the relations the two fruits share. The thought of my bicycle might lead me to think of the table saw it is parked next to in the basement. Through the association of cause and effect, my idea of a struck match leads me to the idea of a flame. The last of these principles of association, of cause and effect, turns out to be faulty for reasons we will examine shortly.

What is the problem with a priori reasoning according to Hume?

The imagination is not merely a source of fancy and fiction. The imagination also includes our ability to understand things when we reason well in formulating new ideas from old ones. A priori reasoning, which is reasoning independent of experience, can produce an understanding of the relations of ideas. Mathematical and logical reasoning is like this. When I recognize the validity of an argument or the logic behind a mathematical proof, the understanding I attain is just a matter of grasping relations between ideas. But a priori reasoning only reveals logical relations between ideas. It tells us nothing about matters of fact. Our ability to understand matters of fact–say truths about the external world–depends entirely on a posteriori reasoning, or reasoning based on experience. As we will see, our ability to reason about matters of fact doesn’t get us very far.

Often our philosophical confusion is the result of having added more than we are entitled to add to our experience when we are striving to understand it. Hume aims to correct many of these errors and, in doing so, he aims to delineate the limits of human knowledge and understanding. As it turns out, we don’t know as much as we commonly suppose, in Hume’s opinion. The result of Hume’s rigorous Empiricism is skepticism about a great many things. Some of Hume’s skeptical results are not so surprising given his Empiricism. Hume is skeptical about objective moral truths, for instance. We don’t get to observe rightness and wrongness in the way we can see colors and shapes, for instance. The idea that there are objective moral truths, according to Hume, is a mistaken projection of our subjective moral sentiments.

Why did Hume distrust theories of causation as some kind of force in nature?

When we examine our everyday idea of causation, Hume says we find four component ideas:

  1. the idea of a constant conjunction of cause and effect (whenever the cause occurs, the effect follows).
  2. the idea of the temporal priority of the cause (the cause happens first, then the effect).
  3. the idea of causes and effects being contiguous (next to each other) in space and time.
  4. the idea of a necessary connection between the cause and the effect.

So, for instance, the idea that striking a match causes it to light is made up of the idea that whenever similar matches are struck (under the right conditions), they light, plus the idea of the striking happening first, and the idea of the striking and the lighting happen right next to each other in time and space, and, finally, the idea that the striking somehow necessitates or makes the match light.

Now let’s consider these component ideas and ask whether they all have an empirical basis in corresponding sense impressions. We do have sense impressions of the first three: the constant conjunction of cause and effect, the temporal priority of the cause, and the contiguity of cause and effect. But Hume argues that we lack any corresponding empirical impression of necessary connections between causes and effects. We don’t observe anything like the cause making the effect occur. As Hume puts the point,

When we look about us towards external objects and consider the operation of causes, we are never able, in a single instance, to discover any power or necessary connexion; any quality, which binds the effect to the cause, and renders the one an infallible consequence of the other. We only find that the one does actually, in fact, follow the other. (An Enquiry Concerning Human Understanding, Section VII)

The idea of causes necessitating their effects, according to Hume’s analysis, is a confused projection of the imagination for which we find no basis in experience. For this reason, Hume denies that we have rational grounds for thinking that causes do necessitate their effects.

How did his distrust of causation lead to his skepticism about our ability to know an external world?

All of our reasoning about the external world is based on the idea of causation. So the skepticism that follows from Hume’s skepticism about causation is quite far-reaching. Our beliefs about the external world, for instance, are based on the idea that things going on in the external world cause our sense impressions. We have no rational grounds for thinking so, says Hume.

More generally, our evidence for what we can know begins with our impressions, the mental representations of sense experience. We assume that our impressions are a reliable guide to the way things are, but this is an assumption we can’t rationally justify. We have no experience beyond our impressions that could rationally certify that our impressions correspond in any way to an external reality. Our assumption that our impressions do correspond to an external reality is a rationally unsupportable product of our imagination.

Why did Hume distrust Inductive reasoning as well?

Closely related to Hume’s skepticism about causation is Hume’s skepticism about inductive reasoning. Inductive arguments, in their standard form, draw a conclusion about what is generally the case, or what will prove to be the case in some as yet unobserved instance, from a limited number of specific observations. The following is an example of a typical inductive argument:

  • Every observed sample of water heated to well over 100 C has boiled.
  • Therefore, whenever water is heated to well over 100 C, it boils.

Unless every instance of water heated to over 100C in the history of the universe is among the observed instances, we can’t be sure that the conclusion is true given the truth of the premises. It follows that strong inductive arguments like the one above are not deductively valid….

How did Hume disrupt the objectivity of the contents of the mind claimed by Berkeley?

Unlike Locke and Berkeley, Hume’s rigorous Empiricism leads him to skepticism about religious matters. To avoid censorship or persecution, critics of religious belief in the 18th century exercised caution in various ways. Hume’s earliest challenge to religious belief, an essay on miracles, was removed from his early work, his Treatise of Human Nature, and published only in his later Enquiries Concerning Human Understanding. In this essay, Hume argues that the belief in miracles can never be rational. A miracle is understood to be a violation of the laws of nature resulting from Divine will. But, argues Hume, the weight of the evidence of our experience overall will always give us stronger reason to mistrust our senses in the case of a seemingly miraculous experience than to doubt the otherwise consistently regular course of events in our experience….

Hume’s last work, his posthumously published Dialogues of Natural Religion, aimed to undermine many arguments for the existence of God, including the Design Argument. According to Hume, the Design Argument is a weak argument by analogy. We have reason to think that machines are the product of human design because we are familiar with their means of production. But we have no analog in the case of the universe. …

In the end, what did Hume believe about the mind itself?

Descartes didn’t hesitate to infer the existence of himself from the certainty of his thinking. And it seems obvious to most of us that having thoughts implies the existence of a subject that thinks. Hume is more cautious on this point.

“For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception.” (Treatise,

The contents of our immediate experience are just particular impressions and ideas. But we have no experience of any single unified self that is the subject of those experiences. The idea of a self, including the idea of the self as a soul, is a fanciful projection from our experiences. All we can say in an empirically grounded way of ourselves, according to Hume, is that we are just a bundle of experiences.

We’ve just given the briefest sketch of how Hume reaches his assorted skeptical conclusions. There are many further arguments and objections to consider, but hopefully, we’ve covered enough to give you an appreciation for how carefully a strict and carefully reasoned Empiricism leads to a variety of skeptical conclusions. Hume’s skepticism about causation and induction may be the most surprising. We often hold up science as the paradigm of human intellectual achievement, and we tend to think of science as pretty empirical. Yet Hume’s strict Empiricism seems to undercut science on the key notions of causation and induction. Perhaps scientific inquiry is not as strictly empirical as Hume’s epistemology. Or perhaps, as some have argued, science can get along fine without induction or causation. Still, if we are not comfortable with Hume’s skepticism about causation and induction, this might give us cause to reconsider his Empiricism. And perhaps also the skepticism about morality it seems to invite. (Payne, Ch 5)

Excerpt from Hume’s An Enquiry Concerning Human Understanding

In the following excerpt, consider:

How does Hume explain the difference between an immediate sensation and other kinds of mental events?

Why are memories or anticipations of experience not the same as experience itself?

Into what two kinds (species) does Hume divide all the events of the mind?

Section II: Of the Origin of Ideas

11. Everyone will readily allow, that there is a considerable difference between the [immediate] perceptions of the mind, when a man feels the pain of excessive heat, or the pleasure of moderate warmth, and when he afterward recalls to his memory this sensation or anticipates it by his imagination. These faculties [i.e., memory and anticipation] may mimic or copy the [original] perceptions of the senses; but they never can entirely reach the force and vivacity of the original sentiment. The most we say of them, even when they operate with greatest vigor, is, that they represent their object in so lively a manner, that we could almost say we feel or see it: But [unless] the mind [is] disordered by disease or madness, they never can arrive at such a pitch of vivacity, as to render these perceptions altogether undistinguishable. All the colors of poetry, however splendid, can never paint natural objects in such a manner as to make the description be taken for a real landskip. The most lively thought is still inferior to the dullest

We may observe a like distinction to run through all the other perceptions of the mind. A man in a fit of anger, is actuated in a very different manner from one who only thinks of that emotion. If you tell me, that any person is in love, I easily understand your meaning…but never [would I confuse that understanding] for the real … passion. When we reflect on our past sentiments and affections, our thought is a faithful mirror, and copies its objects truly; but the colors which it employs are faint and dull, in comparison of those in which our original perceptions were clothed.…

Here therefore we may divide all the perceptions of the mind into two classes or species, which are distinguished by their different degrees of force and vivacity. The less forcible and lively are commonly denominated thoughts or Ideas. The other species [are called] Impressions, employing that word in a sense somewhat different from the usual. By the term impression, then, I mean all our more lively perceptions, when we hear, or see, or feel, or love, or hate, or desire….

Having established the difference between direct Impressions and indirect Ideas in the mind, Hume proceeds in section four of his essay to argue against trusting fully in our understanding.

In what follows, ask:

How does Hume explain why we assume the future will be like the past?

How does he argue that that is a bad assumption to make?

What does this imply for inductive reasoning and science?

Section III: Of the Association of Ideas

Part II.

29. … we always presume, when we see like sensible qualities, that they have like secret powers, and expect that effects, similar to those which we have experienced, will follow from them…

It is [acknowledged everywhere] that there is no known connection between the sensible qualities [what we experience of an object] and the secret powers [its supposed capacity to cause future events]; and consequently, that the mind is not led to form such a conclusion concerning their [always occurring together], by anything which it knows of their nature. As to past experience, it can be allowed to give direct and certain information of those precise objects [then experienced] only, and at that precise period of time, which [the mind then knew]: but why this experience should be extended to future times, and to other objects, which for all we know, may be only in appearance similar; this is the main question on which I would insist. The bread, which I formerly eat, nourished me; that is, a body of such sensible qualities was, at that time, endued with such secret powers: but does it follow, that other bread must also nourish me at another time, and that like sensible qualities must always be attended with like secret powers?

The consequence seems nowise necessary. At least, it must be acknowledged that there is here a consequence drawn by the mind; that there is a certain step taken; a process of thought, and an inference, which wants to be explained. These two propositions are far from being the same, I have found that such an object has always been attended with such an effect, and I foresee, that other objects, which are, in appearance, similar, will be attended with similar effects. I shall allow, if you please, that the one proposition may justly be inferred from the other: I know, in fact, that it always is inferred. But if you insist that the inference is made by a chain of reasoning, I desire you to produce that reasoning. The connection between these propositions is not intuitive.

Doesn’t it seem reasonable to assume that past experience is a good indicator of future experiences? Surely if you consider touching a hot stove you can, based on your past experiences, know that it will burn you, right?

Not so fast, says Hume. Such inductive reasoning is problematic.

32. For all inferences from [past] experience suppose, as their foundation, that the future will resemble the past, and that similar powers will be conjoined with similar sensible qualities. If there be any suspicion that the course of nature may change, and that the past may be no rule for the future, all experience becomes useless, and can give rise to no inference or conclusion. It is impossible, therefore, that any arguments from experience can prove this resemblance of the past to the future, since all these arguments are founded on the supposition of that resemblance. [Even if] the course of things [has up to now been] ever so regular; that alone, without some new argument or inference, proves not that, for the future, it will continue so. …

How to be an Empiricist

Empiricism relies primarily on data to assess a truth claim. First-hand data is, of course, the best, but all mathematically and scientifically gathered data is important to the empiricist and is valued above things like intuition and innate knowledge. The empiricist still uses logic but relies more heavily on inductive arguments rather than deductive arguments. The empiricist wants to examine the data behind any claim. Sensory data, scientific data, and personal observation and experimentation are highly valued. Unless something can be weighed, measured, smelled, and enumerated, the empiricist will remain doubtful. When faced with the claim that the Earth is flat, for example, the Empiricist would want to gather as much data as possible regarding all the possible shapes of the Earth and examine the evidence on all sides. The Empiricist will consider worthy of knowledge whatever the data supports.

Strengths and Weaknesses of Empiricism

Here are some key strengths and weaknesses of empiricism, the philosophical view that knowledge derives from sensory experience rather than innate concepts or reasoning alone:

On the one hand:

  1. Empiricism aligns with the abundant success of science and everyday perception in relying on evidence from the senses.  Empiricism requires us to have experience of the world. Logic alone cannot give us knowledge of how strawberries taste or what love feels like. Only through experiencing the world around us and reflecting on those experiences do we gain knowledge.
  2. It grounds concepts and truths in observable physical realities that can compellingly test theories.  Empiricism seems more concrete than Rationalism, for it relies on factual data to prove why something is true or untrue. Experimentation, measurement, observation, and other scientific ways of gathering data give the empiricist a strong foundation upon which to draw conclusions. In order for something to be true, it must be repeatedly verifiable by scientific methods.
  3. It allows critical external checks on reasoning instead of pure mental introspection vulnerable to error.  Basing our conclusions on experience can show us when we are mistaken. If we believe something that is incorrect, life experience can show us our mistakes and we can revise our beliefs accordingly.

On the other hand:

  1. Linking complex scientific theories to observation has demonstrated difficulties when testing sophisticated models or claims about unobservables.
  2. Abstract and normative concepts like “justice” or “causality” also do not have straightforward sensory correlates.  Some important things cannot be experienced, measured, or observed. The gathering of empirical data cannot always be brought to bear on a problem or claim. There are many things we cannot experience with our senses or objectively measure, like the concepts of rights, justice, or peace. Empiricism runs the risk of positivism (see chapter 8), a theory that reduces all reality to only the perceivable.
  3. Innate cognitive filtering complicates the notion of pure experiencing.   Theory often permeates observation to some degree.  We tend to see what we expect to see.
  4. The foundational role still given by empiricism to the assumed reliability of sensory perception itself remains questionable.  Our senses can be fooled. Human perception can be unreliable, and our methods of observation can be biased and inaccurate, leading to faulty conclusions. Confirmation bias tends to reveal to us only what we assume we will see.
  5. Empiricism lacks resources to critically analyze reasoning approaches themselves as they are applied to interpret observations when devising theories.  Also, data can be manipulated, and experience can vary widely from person to person, leading to conflicting claims about reality. Empiricists sometimes give the impression that data and experience are 100% reliable, yet they disagree amongst themselves about what empiricism can teach us about the world. There was a time when the best empirical evidence showed that the Earth was the center of the solar system and a spirited debate ensued when evidence to the contrary was presented.

So while deeply capturing essential Floor roles for evidence and experiential constraint on credible knowledge sources, empiricism struggles to fulfill totalfoundational needs alone without some rationalist elements or more holistic, integrated models. But provides bedrock grounding.



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PPSC PHI 1011: The Philosopher's Quest by Daniel G. Shaw, Ph.D. is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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