2.2 Rationalist and Empiricists

In this section, we will meet several philosophers, some whose theories exemplify what it means to be a rationalist, and a notable one whose work exemplifies the empiricist’s position. We will get a sense of the conflicts that have prevailed between the proponents of these two theories on how we acquire knowledge of the world.

2.2.1 Plato: Roots of Rationalism

The precedence of the mind and reason over the material world of experience and impressions was a Western philosophical position well before the time of the”continental rationalists” we will examine in this section. Plato (427-347 BCE) was a rationalist. As you will see in the short upcoming videos, for Plato the world of experience held no primacy; what happens in the realm of the sensory and the experiential does not even qualify as “real” much less as a pathway to knowledge. Plato’s “forms” are seen as innate ideas in that the forms/ideas are inborn, within us to be discovered.

Plato’s Forms can be known only through the intellect, and they are the ultimate reality. The world we observe with our senses contains only imperfect copies.


Plato’s theory of Forms is described in the first two minutes of this video. Watch at least that much. Plato’s Best (and Worst) Ideas[CC-BY-NC-ND]
This video provides a quick look at Plato’s cave allegory, which also relates to his theory of Forms. Plato’s Allegory of the Cave. [CC-BY-NC-ND]

2.2.2 Descartes: Continental Rationalism

“Continental rationalism” refers to the work of philosophers on the European continent who, during the 17th and 18th centuries, took exception to the prevailing acceptance of sensory experience as the primary gateway to knowledge. Though some of these rationalists gave sensory experience a place in their theory of knowledge, they regarded reasoning as the only source of dependable knowledge.

Rene Descartes, Baruch Spinoza, Gottfried Wilhelm Leibniz, and Nicolas Malabranche are among the noted continental rationalists. We will look briefly at Rene Descartes’s rationalism, in particular the way in which distrust of sensory perceptions lead him to a position and theory that embraces innate ideas. Later we will meet Gottfried Leibniz.

Rene Descartes (1596-1650) is one of the prominent figures in modern philosophy. His work encompasses not only what we consider philosophical disciplines today, but also the mathematics and science of his times. Such topics were closely aligned with philosophy during his era. His work encompassed methods for seeking knowledge in all disciplines.

Descartes’ work, Meditations on First Philosophy (1641) details his progression through a first-person epistemological drama of realization, from doubt to certainty. He starts from scratch, emptying his mind of every preconception. In the Meditations, we see his rationalist’s confidence in innate ideas.

Note: We will meet Descartes and his Meditations again, in our Metaphysics module where we consider his strict mind-body dualism.

Descartes’ famous wax thought experiment of the Second Meditation describes (among other things) a procedure to “dig out” what is innate. The section of the Second Meditation, imbedded below, also demonstrates Descartes’ doubt about impressions we gather from our senses; they are untrustworthy measures of the nature of physical bodies.

From the Second Meditation: The nature of the human mind and how it is better known than the body. Observe the dramatic first-person style of the Meditations.

Let us now accordingly consider the objects that are commonly thought to be the most easily, and likewise the most distinctly known, viz., the bodies we touch and see; not, indeed, bodies in general, for these general notions are usually somewhat more confused, but one body in particular. Take, for example, this piece of wax; it is quite fresh, having been but recently taken from the beehive; it has not yet lost the sweetness of the honey it contained; it still retains somewhat of the odor of the flowers from which it was gathered; its color, figure, size, are apparent (to the sight); it is hard, cold, easily handled; and sounds when struck upon with the finger. In fine, all that contributes to make a body as distinctly known as possible, is found in the one before us. But, while I am speaking, let it be placed near the fire—what remained of the taste exhales, the smell evaporates, the color changes, its figure is destroyed, its size increases, it becomes liquid, it grows hot, it can hardly be handled, and, although struck upon, it emits no sound. Does the same wax still remain after this change? It must be admitted that it does remain; no one doubts it, or judges otherwise. What, then, was it I knew with so much distinctness in the piece of wax? Assuredly, it could be nothing of all that I observed by means of the senses, since all the things that fell under taste, smell, sight, touch, and hearing are changed, and yet the same wax remains. It was perhaps what I now think, viz., that this wax was neither the sweetness of honey, the pleasant odor of flowers, the whiteness, the figure, nor the sound, but only a body that a little before appeared to me conspicuous under these forms, and which is now perceived under others. But, to speak precisely, what is it that I imagine when I think of it in this way? Let it be attentively considered, and, retrenching all that does not belong to the wax, let us see what remains.

There certainly remains nothing, except something extended, flexible, and movable. But what is meant by flexible and movable? Is it not that I imagine that the piece of wax, being round, is capable of becoming square, or of passing from a square into a triangular figure? Assuredly such is not the case, because I conceive that it admits of an infinity of similar changes; and I am, moreover, unable to compass this infinity by imagination, and consequently this conception which I have of the wax is not the product of the faculty of imagination. But what now is this extension? Is it not also unknown? for it becomes greater when the wax is melted, greater when it is boiled, and greater still when the heat increases; and I should not conceive clearly and according to truth, the wax as it is, if I did not suppose that the piece we are considering admitted even of a wider variety of extension than I ever imagined. I must, therefore, admit that I cannot even comprehend by imagination what the piece of wax is, and that it is the mind alone which perceives it. I speak of one piece in particular; for as to wax in general, this is still more evident. But what is the piece of wax that can be perceived only by the understanding or mind? It is certainly the same which I see, touch, imagine; and, in fine, it is the same which, from the beginning, I believed it to be. But (and this it is of moment to observe) the perception of it is neither an act of sight, of touch, nor of imagination, and never was either of these, though it might formerly seem so, but is simply an intuition (inspectio) of the mind, which may be imperfect and confused, as it formerly was, or very clear and distinct, as it is at present, according as the attention is more or less directed to the elements which it contains, and of which it is composed.

This brief passage demonstrates the inadequacy of both sensory impressions and imagination. Both the ideas we derive from sensory impressions and those we fabricate by imagination figure in Descartes’s distinctions among types of ideas. His argument for innate ideas involves his overall classification of ideas as being one of three types: adventitious (derived from the world outside us via sensation), factitious (created by the imagination), and innate (concepts that are clear and distinct truths.) Descartes’s argument that clear and distinct truths are innate is arrived at by eliminating the possibility for such ideas being either factitious (mentally fabricated) or adventitious (based on experience.) They are eternal truths.

Descartes Summary

A rationalist, in the Platonic tradition of innate ideas, Descartes believed that knowledge derives from ideas of the intellect, not from the senses. His argument for innate ideas involves his elimination of the possibility that clear and distinct ideas can be gained either through experience or imagination. Innate ideas have universal truth and are the only dependable source of knowledge. Clear and distinct in our minds, innate ideas are universal truths. The idea of a triangle with its requisite properties, for example, can be perceived clearly and distinctly within the mind, without reference to a particular object in the world.

Several supplementary reading resources (bottom of page) provide insight on innate ideas as an element of Descartes’ s rationalism.


Do you think that innate ideas are possible? Putting it another way, do you think that we have ideas or knowledge not based on experience? Provide your reasons/argument for your position.

Note: Post your response in the appropriate Discussion topic

2.2.3 Locke: British Empiricism

“British empiricism” refers to a philosophical direction during the 17th and 18th centuries, primarily in the British Isles. This movement is characterized by its rejection of and response to tenets of rationalism such as innate ideas and knowledge based on anything a priori. Francis Bacon, whose lifetime overlapped with that of Descartes, was an early figure in this movement. In the 18th century, John Locke, George Berkeley and David Hume became the leading figures. We will examine John Locke’s statement of the empiricist’s position that experience is the only viable basis of knowledge.

John Locke (1632-1704) produced a comprehensive and influential philosophical work with his An Essay concerning Human Understanding in 1690. This work sets out to provide a comprehensive account of the mind and how humans acquire knowledge. An important and primary part of his agenda is to dispute the foundations of the rationalist theory of knowledge, including the possibility that there could be innate ideas. Locke’s project with the Essay, however, is a lot larger than an attack on nativism (innate ideas.) His intention is to thoroughly examine the process of understanding and acquisition of knowledge, to describe exactly how our minds work.

Locke describes two distinct types of experience: (1) outer experience is acquired through our five senses and involves objects that exist in the world; and (2) inner experience is derived from mental acts such as reflection. The latter are complicated. But all ideas, regardless of their complexity are constructed from combinations of simple ideas, the building blocks for everything we could possibly think. All ideas (and all knowledge) originate from experience. Our minds start off as blank slates.

Part of Locke’s argument against innate ideas is that they are not universal – not everyone has them. This excerpt from Book I, Chapter 1 of the Essay adds the additional important argument against the possibility of innate ideas, questioning the possibility of having ideas in your mind without knowing they are there.

5. Not on Mind naturally imprinted, because not known to Children, Idiots, etc.

For, first, it is evident, that all children and idiots have not the least apprehension or thought of them. And the want of that is enough to destroy that universal assent which must needs be the necessary concomitant of all innate truths: it seeming to me near a contradiction to say, that there are truths imprinted on the soul, which it perceives or understands not: imprinting, if it signify anything, being nothing else but the making certain truths to be perceived. For to imprint anything on the mind without the mind’s perceiving it, seems to me hardly intelligible. If therefore children and idiots have souls, have minds, with those impressions upon them, THEY must unavoidably perceive them, and necessarily know and assent to these truths; which since they do not, it is evident that there are no such impressions. For if they are not notions naturally imprinted, how can they be innate? and if they are notions imprinted, how can they be unknown? To say a notion is imprinted on the mind, and yet at the same time to say, that the mind is ignorant of it, and never yet took notice of it, is to make this impression nothing. No proposition can be said to be in the mind which it never yet knew, which it was never yet conscious of…

Locke Summary

John Locke was an empiricist who believed that the mind is a blank slate (tabula rasa) when we are born; the mind contains no innate ideas. He thought that we gain all of our knowledge through our senses. Locke argued against rationalism by attacking the view that we could know something and yet be unaware that we know it. He thought it was contradictory to believe we possess knowledge of which we are unaware. He also maintained that innate ideas would be universal by definition and that there are people who could not have such ideas.

A supplementary reading resource (bottom of page) explores the overall project of Locke’s Essay concerning Human Understanding.

2.2.4 Leibniz: A Rationalist Response to Empiricism

Gottfried Wilhelm Leibniz (1646-1716) was a continental rationalist, whose response to Locke’s attack on innate ideas, takes exception with Locke’s thesis that “nothing can be in the mind which is not in consciousness.” Leibniz’s reply to Locke is part of his 1704 work, New Essays on Human Understanding.

Note: Leibniz’s conception of the nature of consciousness is at odds with that of Locke. For Locke, consciousness and the soul are one and the same – immaterial and unobservable, unlike the experiential world. (This is a dualistic viewpoint put forward by Descartes and has been commonly held.) For Leibniz, consciousness is real in the same way the world is, but it is not “mechanical.” We will return to the topic of dualism in the module on Metaphysics.

Leibniz’s response to Locke is addressed here in a second-source work by American philosopher John Dewey (1859 – 1952). This excerpt is from the end of Chapter IV of Dewey’s book, Leibniz’s New Essays Concerning the Human Understanding: A Critical Exposition, 1888:

He [Locke] founds his denial of innate ideas not only upon a static conception of their ready made existence”in” the soul, but also upon an equally mechanical conception of consciousness.”Nothing can be in the mind which is not in consciousness.” This statement appears axiomatic to Locke, and by it he would settle the whole discussion. Regarding it, Leibniz remarks that if Locke has such a prejudice as this, it is not surprising that he rejects innate ideas. But consciousness and mental activity are not thus identical. To go no farther, the mere empirical fact of memory is sufficient to show the falsity of such an idea. Memory reveals that we have an indefinite amount of knowledge of which we are not always conscious. Rather than that knowledge and consciousness are one, it is true that actual consciousness only lays hold of an infinitesimal fraction of knowledge. But Leibniz does not rely upon the fact of memory alone. We must constantly keep in mind that to Leibniz the soul is not a form of being wholly separate from nature, but is the culmination of the system of reality…….

….Leibniz not only denies the equivalence of soul and consciousness, but asserts that the fundamental error of the psychology of the Cartesians (and here, at least, Locke is a Cartesian) is in identifying them. He asserts that”unconscious ideas” are of as great importance in psychology as molecules are in physics. They are the link between unconscious nature and the conscious soul. Nothing happens all at once; nature never makes jumps; these facts stated in the law of continuity necessitate the existence of activities, which may be called ideas, since they belong to the soul and yet are not in consciousness.

When, therefore, Locke asks how an innate idea can exist and the soul not be conscious of it, the answer is at hand. The”innate idea” exists as an activity of the soul by which it represents—that is, expresses—some relation of the universe, although we have not yet become conscious of what is contained or enveloped in this activity. To become conscious of the innate idea is to lift it from the sphere of nature to the conscious life of spirit. And thus it is, again, that Leibniz can assert that all ideas whatever proceed from the depths of the soul.…… An innate idea is now seen to be one of the relations by which the soul reproduces some relation which constitutes the universe of reality, and at the same time realizes its own individual nature..…

Leibniz’s argument against Locke, as explained by Dewey, has psychological underpinnings; the mere concept of memory implies that we have ideas that are not conscious at a given moment. Leibniz conceived innate ideas as dispositions or tendencies that are necessary truths from which the mind thrives and flourishes.

Leibniz Summary

According to Leibniz, who was a rationalist, we do have innate ideas, which start as tendencies. Initially these innate ideas are unconscious ideas; they represent “some relation of the universe” and become fully formed (conscious) as we experience the world. Leibniz argued that sense experience only gives us examples, contingent truths, but never the necessary principles we attach to those examples.

A supplemental resource is available (bottom of page) on Leibniz conception of innate ideas.


This TED Talk speaker, psychologist Stephen Pinker, argues against the idea that the mind begins as a”blank slate.” Viewing it may be helpful in formulating your response to the Coursework question below. Human Nature and the Blank Slate[CC-BY-NC-ND]


John Dewey tells us that Gottfried Leibniz, in defense of his theory of innate ideas, “asserts that ‘unconscious ideas’ are of as great importance in psychology as molecules are in physics.” And “To become conscious of the innate idea is to lift it from the sphere of nature to the conscious life of spirit.”

What do you think of this psychological perspective on innate ideas? Does it seem predictive of modern thinking about the mind, (for example Stephen Pinker)? (100-200 words)

Note: Submit your response to the appropriate Assignments folder.

Supplemental Resources


This video emphasizes how Plato’s Theory of Forms is not just about acquiring knowledge (epistemology) but also about the nature of reality itself (metaphysics.) PLATO ON: The Forms


Stanford Encyclopedia of Philosophy (SEP) Descartes’ Epistemology Read section 1.5. This brief section explains how Descartes’ conception of innate ideas resembles Platonic Forms.
Internet Encyclopedia of Philosophy (IEP) Continental Rationalism Read section 2.a. It is a very brief discussion of Descartes’ conception of innate ideas.


Internet Encyclopedia of Philosophy (IEP) John Locke (1623-1704) Read this article’s introduction and section 2, a, b, and c for a larger account of the project of Locke’s Essay. 


Stanford Encyclopedia of Philosophy (SEP) Gottfried Wilhelm Leibniz: Innate Ideas Read section 6.3 on innate ideas. You will notice that Leibniz theory of knowledge is closely interwoven with his theory on the nature of reality (his metaphysics).