4.2.2 Rationalism

Except for our own thoughts, there is nothing absolutely in our power. – Rene Descartes

Rationalism is a school in Western philosophy that holds the view that reason is the chief source and test of knowledge. Rationalists hold that reality itself has an inherently logical structure and that a class of truths exists that the intellect can grasp directly. The mind, say the Rationalists, is able to grasp certain truths intuitively as “self-evident” and from these intuitions use reasoning to come to other clear truths.

Generally speaking, this direct apprehension of an intuitive truth is a kind of a priori knowledge or belief that is characterized by its immediacy; a form of rational insight, the light bulb going off in the mind. Suddenly our minds simply “see” something in such a way as to give us an undeniable belief. This was the kind of “Aha!” moment Descartes experienced with the cogito ergo sum or the “Eureka!” (Gr.: “I have found it!”) supposedly shouted by Archimedes after he had stepped into a bath and noticed that the water level rose, whereupon he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged.

Starting from these kinds of direct intuitions of truth, Rationalists go on to use deductive reasoning to argue for other truths. The fundamental axioms of mathematics or logic are good examples. It is not necessary, for example, to “prove” that a whole is greater than one of its parts, or that the ends of a line are points. These maxims are taken to be axiomatic, given, self-evident, unquestionable truths.

Thus, the mind is capable, say the Rationalists, of a kind of “innate” knowledge that allows it to come to truths without sensory experience. For example, consider the statement “a triangle is a plane figure with three straight sides and three angles.” We can know this without experiencing a triangle drawn on paper. (In fact, no triangle drawn on paper is a triangle. It is only a perceptual image of the concept of triangularity). We know triangularity by definition. The concept need not be perceived to be understood.

Rationalists believe we have an innate rational nature. Our experiences may trigger a process by which we bring this knowledge to consciousness, but the experiences do not provide us with the knowledge itself, which has in some way been with us all along. Early rationalists like Plato claimed that we obtained this innate knowledge in an earlier existence and others that God provided us with it at creation. More contemporary rationalists see it as built into the rational structures of the mind.

For example, Gottfried Wilhelm Leibniz suggested that we are born with certain innate ideas, the most identifiable of these being mathematical truisms. The idea that 1 + 1 = 2 is evident to us without the necessity for empirical evidence. Leibniz argues that empiricism can only show us that concepts are true in the present; the observation of one apple and then another in one instance, and in that instance only, leads to the conclusion that one and another equals two. However, the suggestion that one and another will always equal two requires an innate idea, as that would be a suggestion of things unwitnessed.

Leibniz called such concepts as mathematical truisms “necessary truths”. Another example of such may be the phrase, “what is, is” or “it is impossible for the same thing to be and not to be”. Leibniz argues that such truisms are universally assented to (acknowledged by all to be true); this being the case, it must be due to their status as innate ideas. Often there are ideas that are acknowledged as necessarily true but are not universally assented to. Leibniz would suggest that this is simply because the person in question has not become aware of the innate idea, not because they do not possess it. Leibniz argues that empirical evidence can serve to bring to the surface certain principles that are already innately embedded in our minds. This is similar to needing to hear only the first few notes in order to recall the rest of the melody.

Rationalists will trust these innate ideas or intuitions far more than the data given us by our senses.

Rationalism in Ancient Greece: Plato

Rationalism is another school of epistemology that dates back to the ancient Greeks. Plato, Socrates’ most famous student, recorded the teachings of his master in the form of dialogues between Socrates and his opponents. Plato’s dialogues are our primary source of knowledge for Socrates. However, it is difficult often to separate Socrates’ ideas from those of Plato. Either way, it is clear that both were proponents of reason, not sensation, as a means of getting to the truth.

Rationalists distrust the information we get from our senses. Our senses are so often deceived. The only kind of information we can truly trust is what we can know with our minds alone. Plato spoke of these certain mental realities as “Ideas” or “Forms” or “Universals.” They exist, he said, above and beyond the senses and are necessary for our minds to have knowledge at all.

He, therefore, looked to such disciplines as mathematics and music theory with their seeming clarity and non-reliance upon the senses as models for how to get to certain knowledge. These disciplines sought to come to a priori truths not through experimentation or observation but entirely by means of mental calculations.

In his dialogue Meno, Socrates insists that all “new” learning is really nothing more than remembering (Gr.: anamnesis) what we have already learned in prior lifetimes.

SOCRATES: So, with virtue now. I don’t know what it is. … Nevertheless, I am ready to carry out, together with you, a joint investigation and inquiry into what it is.

MENO: But how will you look for something when you don’t in the least know what it is? How on earth are you going to set up something you don’t know as the object of your search? To put it another way, even if you come right up against it, how will you know that what you have found is the thing you didn’t know?

SOCRATES: I know what you mean…. Those who tell it are priests and priestesses of the sort … say that the soul of man is immortal. At one time it comes to an end–that which is called death–and at another is born again but is never finally exterminated. … Thus, the soul, since it is immortal and has been born many times and has seen all things both here and in the other world, has learned everything that is. So, we need not be surprised if it can recall the knowledge of virtue or anything else which, as we see, it once possessed. All nature is akin, and the soul has learned everything, so that when a man has recalled a single piece of knowledge–learned it, in ordinary language–there is no reason why he should not find out all the rest, if he keeps a stout heart and does not grow weary of the search, for seeking and learning are in fact nothing but recollection. (Meno 80c-81e).

Note in particular Meno’s question here. How is it that you can learn a new thing if you have never experienced it before? Must you not at least know the “kind” of thing it is before you discover it? For example, if I asked you to go out and purchase a “nexgen flither,” it is highly unlikely you will comb through the store shelves and find what I ask. You would not even know which kind of store to shop in, because you do not know the “kind of thing” this nexgen flither is. Your eyes may indeed pass over it, mind you, but not knowing what you are looking for, they will not “see” it. For this reason, Rationalists insist that a priori knowledge is required for perception itself. Sense data alone is insufficient.

Now you might argue that there is no such thing as a nexgen flither! However, if you were a scientist from three centuries ago and someone asked you to find a platypus you might well have said the same. In fact, without some definitions (semiaquatic, egg-laying mammal) no one would have discovered such a creature. So too with nexgen flither, you would need to know the “kind of thing” it is before you could find it.

Rationalism relies on the idea that reality has an underlying structure that can be grasped through mathematical and logical principles, innate ideas, and definitions, and not simply through sense experience. Rather than being a blank slate to be imprinted with sense data, the mind is structured by, and subject to analysis by, these innate ideas and by logical methods of reasoning.

Rationalism in Early Modern Europe: Descartes, Spinoza, and Leibnitz.

Let’s look at the ideas of three important early modern rationalists. Each believed that the mind contained some basic or innate knowledge that was essential for understanding the world. They reasserted Plato’s notion that we have within our mind’s fundamental principles or categories of “innate ideas” which do not come from our experience of the world but are built into the human mind itself, a priori, or prior to experience.

Descartes

When we explored his “Methodological Doubt” technique in the section on Skepticism we saw that Descartes was seeking a foundation in the realm of mind on which to build a new edifice of philosophy. Descartes is said to be the father of modern philosophy because he broke with the past. First, he seems to have wanted to start his philosophy from scratch, not depend upon past thinkers and authorities. He resolved to rely on reason alone, not appeals to past work. Second, he wished to avoid the conjectures and speculations of the medieval Scholastics and chose to work only with clear and self-evident ideas. Third, his new philosophy would not be formed around scriptures or traditions but instead be built upon the bedrock of these clear and distinct ideas.

Innate ideas for Descartes

But what constitutes a “clear and distinct” or an “innate” idea for Descartes? He did not accept Plato’s contention that we are born with innate knowledge. According to the historian of philosophy Frederick Copleston, for Descartes,

Such ideas are not, indeed, innate in the sense that they are present in the baby’s mind as fully-fledged ideas. But the mind produces them, as it were, out of its own potentialities on the occasion of experience of some sort. It does not derive them from sense experience…. Descartes was no empiricist. But sense-experience can furnish the occasion on which these ideas are formed (Copleston, Hist of Phil IV, pp 67-68).

These ideas, not derived from our sense-experience or from our imagination, are instead,

… instances of your mind’s actualization of its inner potentiality. It can hardly be claimed, I think, that Descartes provided a clear, positive account of the nature and genesis of innate ideas. But… he considered ideas of this third class to be virtually innate, implanted in the mind by nature or, more properly, by God (Copleston, p. 84).

For Descartes, there were two distinct realities or substances: the mind which deals with innate ideas and self-evident ideas, and matter, which forms the body and the physical universe. We will return to this distinction in a later chapter. for now, it’s important to note that Descartes believed the mind to be a radically different kind of thing from matter and for purposes of knowledge was far more trustworthy than the always deceiving sense data impressions we receive from the world.

From the very beginning of his research, Descartes aimed at exploring the competence of thought in ascertaining knowledge, and in doing so he wrote Rules for the Direction of the Mind in search of assurance in science. This view would later be called “rationalism” because he prioritized the functions of intellect, imagination, sense perception, and memory. Rationalism influenced a long line of philosophers from the modern era throughout the contemporary era in philosophy. He later recommended a reduction of human knowledge from simple concepts and propositions. This method, as expounded in Rule XII, relies on the human mind as a “power.” He states:

As for the objects of knowledge, it is enough if we examine the following three questions: What presents itself to us spontaneously? How can one thing be known on the basis of something else? What conclusions can be drawn from each of these?

Notice his emphasis on the understanding of objective knowledge. The question is not “What is it?” but “How does it appear to me?” and “How does it connect with what I know?” Investigating the nature of the mind is of primary importance. Knowledge of objects themselves takes a back seat to the inner workings of the mind.

Descartes describes the intellect as “the power through which we know things in the strict sense [that] is purely spiritual and is … distinct from the whole body.” To explain this power is difficult; Descartes explains that “nothing quite like this power is to be found in corporeal things.” It is the intellect that applies itself to seeing, touching, and so on; and only it can “act on its own,” that is, [can] understand (Blum, “Substance Dualism in Descartes,” in Salazar et.al. Introduction to Philosophy: Philosophy of Mind).

Excerpts from Descartes’ Meditations on First Philosophy

Meditation II–OF THE NATURE OF THE HUMAN MIND; AND THAT IT IS MORE EASILY KNOWN THAN THE BODY.

I am, therefore, precisely speaking, only a thinking thing, that is, a mind (mens sive animus), understanding, or reason, terms whose signification was before unknown to me. I am, however, a real thing, and really existent; but what thing? The answer was, a thinking thing. …

But what, then, am I? A thinking thing, it has been said. But what is a thinking thing? It is a thing that doubts, understands, [conceives], affirms, denies, wills, refuses; that imagines also, and perceives.

Assuredly it is not little if all these properties belong to my nature. But why should they not belong to it? Am I not that very being who now doubts of almost everything; who, for all that, understands and conceives certain things; who affirms one alone as true, and denies the others; who desires to know more of them, and does not wish to be deceived; who imagines many things, sometimes even despite his will; and is likewise percipient of many, as if through the medium of the senses. Is there nothing of all this as true as that I am, even although I should be always dreaming, and although he who gave me being employed all his ingenuity to deceive me? Is there also any one of these attributes that can be properly distinguished from my thought, or that can be said to be separate from myself? For it is of itself so evident that it is I who doubt, I who understand, and I who desire, that it is here unnecessary to add anything by way of rendering it more clear. And I am as certainly the same being who imagines; for although it may be (as I before supposed) that nothing I imagine is true, still the power of imagination does not cease really to exist in me and to form part of my thought. In fine, I am the same being who perceives, that is, who apprehends certain objects as by the organs of sense, since, in truth, I see light, hear a noise, and feel heat. But it will be said that these presentations are false, and that I am dreaming. Let it be so. At all events it is certain that I seem to see light, hear a noise, and feel heat; this cannot be false, and this is what in me is properly called perceiving (sentire), which is nothing else than thinking.

From this I begin to know what I am with somewhat greater clearness and distinctness than heretofore. But, nevertheless, it still seems to me, and I cannot help believing, that corporeal things, whose images are formed by thought [which fall under the senses], and are examined by the same, are known with much greater distinctness than that I know not what part of myself which is not imaginable; although, in truth, it may seem strange to say that I know and comprehend with greater distinctness things whose existence appears to me doubtful, that are unknown, and do not belong to me, than others of whose reality I am persuaded, that are known to me, and appertain to my proper nature; in a word, than myself.

Spinoza

Baruch Spinoza (1632-1667) was a Dutch philosopher from a Jewish family. One of the early thinkers of the Enlightenment and a modern scholar of the Bible, he came to be considered one of the great rationalists of the 17th century. Inspired by the groundbreaking ideas of Descartes, Spinoza became a leading philosophical figure of the Dutch Golden Age.

Spinoza, like Descartes, was enthralled with the clarity of mathematical concepts and the apparent certainties of mathematics. For his trade, he was a lens maker, and the science of optics required an advanced understanding of geometry. But Spinoza used mathematics as a way of describing all things.

He contended that everything that exists in Nature (i.e., everything in the Universe) is one Reality (substance) and there is only one set of rules governing the whole of the reality that surrounds us and of which we are part. Spinoza viewed God and Nature as two names for the same reality, namely a single, fundamental substance (meaning “that which stands beneath” rather than “matter”) that is the basis of the universe and of which all lesser “entities” are actually modes or modifications [of that one reality].

Innate ideas for Spinoza

Spinoza does not speak of innate ideas per se as Descartes and Leibniz do, however, he uses the term “common notions” to imply the same kind of fundamental, a priori frameworks in the mind.

The mind, for Spinoza, just by virtue of having ideas, which is its essence, has ideas of what Spinoza calls “common notions,” or in other words, those things which are “equally in the part and in the whole.” Examples of common notions include motion and rest, extension, and indeed God. Take extension for example. To think of any “body” – however small or however large – is to have a perfectly complete idea of extension. So, insofar as the mind has any idea of “body” (and, for Spinoza, the human mind is the idea of the human body, and so always has ideas of body), it has a perfectly adequate idea of extension. The same can be said for motion and rest. The same can also be said for God, except that God is not equally in the part and in the whole of extension only, but of all things. Spinoza treats these common notions as principles of reasoning. Anything that can be deduced on their basis is also adequate. Thus, he rejects Descartes’s separation of mind from the universe and writes of a universal mind/pattern of thought behind all that we can experience (Homan, “Continental Rationalism,” IEP).

This notion of a universal pattern underlying all things hearkened back to ancient Greek ideas like those of Pythagoras, who believed everything was constituted by number, and the Stoics who saw in all of nature a divine logos or rationality.

Spinoza would be thrilled by the efforts of current physicists to discover the mathematics behind a Unified Theory that would reconcile all known forces of nature. As PBS has said,

We have reached an extraordinary point in the history of science, for some physicists believe they are now on the verge of having a single theory that will unite all of their science under one mathematical umbrella. In particular, this theory would unify the two great bastions of twentieth-century physics – the general theory of relativity and quantum theory. Since general relativity describes the large-scale, or cosmological structure of the universe, and quantum theory describes the microscopic, or subatomic, structures, the unification of these theories would explain both the very big and the very small. This theory is often referred to as a “theory of everything”.

In particular, this theory would unify our understanding of all the fundamental physical forces in our universe. There are four such forces that physicists currently recognize: gravity (which keeps planets revolving around their suns, and is responsible for the formation of stars and galaxies), the electromagnetic force (which is responsible for light, heat, electricity, and magnetism; and which is also responsible for holding atoms together), the weak nuclear force (which acts inside atomic nuclei and is responsible for a certain kind of radioactive decay), and the strong nuclear force (which holds together the protons and neutrons in atomic nuclei and is therefore crucial to the stability of matter). At the moment, physicists have separate theories for each of these forces, but they would like one unified theory of all four. That goal has partly been realized in that they now have a theory that unifies two of these forces – the electromagnetic and weak forces – but unifying all four is proving to be extremely difficult. Nonetheless, most … physicists are confident this goal will be realized in the next few decades.

PBS – A Theory of Everything

Leibnitz

Gottfried Wilhelm (von) Leibniz (1646–1716) was a German polymath active as a mathematician, philosopher, scientist, and diplomat. He is a prominent figure in both the history of philosophy and the history of mathematics. He wrote works on philosophy, theology, ethics, politics, law, history, and philology. Leibniz also made major contributions to physics and technology, and anticipated notions that surfaced much later in probability theory, biology, medicine, geology, psychology, linguistics, and computer science. He also contributed to the field of library science: while serving as overseer of the Wolfenbüttel library in Germany, he devised a cataloging system that would have served as a guide for many of Europe’s largest libraries.

Among quite a few other things, Leibniz was an important mathematician. He and Newton vied for credit for discovering the calculus of infinitesimals. He was also politically active as an advisor to assorted rulers and aristocrats. Like Descartes, Leibniz was, at least publicly, religious. His grandest political ambition was to see the Christian church re-unified (recall that Protestants had broken off from Catholics over the prior few centuries). Leibniz was arguably the first to have imagined anything like information technology. Among his grand ambitions was to formulate a universal symbolic language for science and philosophy that would be rigorously rule-driven and free of all ambiguity. He even got as far as constructing a calculating machine, though not a very reliable one. … (Payne, Ch. 4).

As a Rationalist, Leibniz also accepted the concept of innate ideas (a priori). In the excerpt below, notice how he connects reason and innate ideas.

Excerpts from Leibniz’ La Monadologie

Logic also has many such truths, and so do metaphysics and ethics. . . .and so the proof of them can only come from inner principles, which are described as innate. It would indeed be wrong to think that we can easily read these eternal laws of reason in the soul. . .. without effort or inquiry; but it is enough that they can be discovered inside us if we give them our attention: the senses provide the prompt, and the results of experiments also serve to corroborate reason, rather as checking procedures in arithmetic help us to avoid errors of calculation in long chains of reasoning. This is how man’s knowledge differs from that of beasts (Leibniz, New Essays on Human Understanding, Preface, Gutenberg).

I don’t base the certainty of innate principles on universal consent; for I have already told you that I think we should work to find ways of proving all axioms except primary ·or basic· ones. I grant you also that a very general but not universal agreement could come from something being passed on from person to person throughout the whole of mankind; the practice of smoking tobacco has been adopted by nearly all nations in less than a century.  Some able people. . .. have believed that knowledge of God came in that way from a very old and very widespread word-of-mouth process, and I’m willing to believe that knowledge of God has indeed been confirmed and amended by teaching. But it seems that nature has helped to bring men to it without anyone teaching them: the wonders of the universe have made them think of a higher power. . .. Nations have been found that fear invisible powers, though they seem not to have learned anything else from any other societies. Of course, their fear of invisible powers doesn’t bring them the whole way to the idea of God that we have and require; but that idea too, as we shall see, is in the depth of our souls without having been put there ·along the way (Leibniz).

How to be a Rationalist

When considering a truth claim, the rationalist relies primarily on an assessment of the logic of an argument to determine how convincing it is. The rationalist wants to examine the argument to see if it is valid (do the premises support the conclusion?) and if it comes to a logical conclusion.

Rationalism does NOT mean that things like sensory data, scientific or empirical data, or personal experience are ignored. The rationalist needs this type of data and experience to evaluate the premises of a claim – they’re just not the most important. Empirical evidence is insufficient if the argument remains invalid. Rationalists accept things like intuition, deduction, and innate ideas as primary and more convincing of truth than sensory evidence.

When faced with the claim that the Earth is flat, for example, the Rationalist would first examine the structure of the argument. Are the premises true or false? Do the premises provide support for the conclusion? If the premises are found to be faulty, or if the premises do not support the conclusion, then the argument is invalid, and the Rationalist will not find the claim to be convincing.

Strengths and Weaknesses of the Rationalist Approach

Here are some of the main perceived strengths and weaknesses of rationalist approaches in epistemology that emphasize logical reasoning and conceptual analysis as the source of knowledge:

On the one hand:

1. Rathionalism aligns with the power of reason to derive systems of mathematical, logical and some philosophical truths introspectively.  Rationalism is right to look for the reasons why something is true. Rationalism examines the premises supporting a claim. For example, an object thrown upward will return to the ground because there are physical laws that govern gravity, not because a million people have seen it happen. Rationalism looks for principles that are independent of human sensory perception.
2. It provides foundations for knowledge that are self-evident or otherwise internally justified without depending on experiential confirmation. Our senses can and do fool us and our perceptions can fail us, but the light of pure logic and reason is reliable. Without reason, our sensory experience would be overwhelming and chaotic. When we view a magic show, our senses are being fooled. Only through the use of reason are we able to understand what is happening and not be tempted to believe that the performer really has magical powers.
3. The certainty and necessity attributed to logically deduced truths or rational intuitions fits with their seemingly undoubtable apparent nature.  Some truths about the world can only be discovered through the use of reason. Humans are uniquely able to conceptualize. We seem to come pre-wired with certain innate concepts built in. For example, consider the concept of peace. We cannot weigh, measure, taste, touch or smell peace because it is not a physical thing, it is a concept. We know when we are at peace, or when we are not, but only because we can reason about the concept.
4. If sound, rationalism provides an autonomous basis for human knowledge grounded in the essential capabilities of the intellect.  Rationalists believe that there is a reason for the existence of each object or phenomenon. The reason an object comes back to the ground when thrown upwards is because of a (rational) law of gravity, not because a million people have observed objects falling. Rationalism tries to find the general principles behind each phenomenon that exist whether humans know them yet or not. These principles are independent of human perceptions.
5. It offers a way to avoid the infinite regress challenges of skepticism.

On the other hand:

1. Rationalism likely overstates the ability of reason to reach into metaphysical, empirical and value domains where conceptual inquiries have uncertain conclusions.  Rationalism has often been accused of neglecting the importance of experience. Take strawberries for example. We can use reason to examine some of the properties of a strawberry, but how will you know how it tastes unless you eat one? And how will you know whether or not strawberries are delicious without experience?
2. It aligns poorly with the dependency of advanced reasoning itself on external influences like acquired linguistic systems, methods and background knowledge.
3. It isolates rational faculties in ways modern psychology and neuroscience have trouble validating empirically.
4. It Typically assumes controversial innate mental content and truth-reliability of reason without sufficient critical argument.  The use of pure reason, however, can lead to conflicting claims about truth and reality. Rationalists often give the impression that reason will provide us with knowledge of what is real and true. However, Rationalists themselves often arrive at conflicting claims. For example, Descartes believed that reason pointed to the existence of the Christian conception of God. Spinoza comes to a completely different conclusion and ends up accused of atheism because of his assertion that pantheism was the rational conclusion.  Our logic is not infallible. Our ways of thinking about the world are sometimes based on human misconceptions. Heavier-than-air flight was thought to be rationally absurd until the Wright brothers proved that it was possible.

So while properly highlighting a fundamental role for reason in deriving systems of necessary truths, as a fully general knowledge source rationalism makes excessive aspirations of capability and justificatory independence from experiential constraints.

Works Cited

“Baruch Spinoza / E. Hader Pinxit ; Phot. u. Verl. v. Sophus Williams, Berlin W.” Library of Congress, 1 Jan. 1884, https://loc.getarchive.net/media/baruch-spinoza-e-hader-pinxit-phot-u-verl-v-sophus-williams-berlin-w. Accessed 17 May 2022.

Edelinck, Gerard. “René Descartes.” Wikimedia Commons, 1707, https://commons.wikimedia.org/wiki/File:Portrait_of_René_Descartes,_bust,_three-quarter_facing_left_in_an_oval_border,_(white_background_removed).png. Accessed 17 May 2022.

Francke, Christoph Bernhard. “Portrait of Gottfried Leibniz (1646-1716), German Philosopher.” Wikimedia Commons, 1695, https://commons.wikimedia.org/wiki/File:Christoph_Bernhard_Francke_-_Bildnis_des_Philosophen_Leibniz_(ca._1695).jpg. Accessed 17 May 2022.