How Do We Know: Sense Perception (Part II: Locke On Innate Knowledge)

Descartes was a monumental turning point in the history of Western philosophical and scientific thought. But the revolution did not stop with him. The project he began, and the questions he asked, were taken up after him by various thinkers in the next few centuries, with significantly differing results.

Descartes himself was a “rationalist,” and is often considered “the father of modern rationalism” [1]. Rationalism is an approach to epistemology which holds “that there are certain truths that can be known by reason alone, independently of sense experience” [2]. In other words, we can have have a priori knowledge which is not received from the external world but is in some way “built in” to our rational faculties. Here is a concise explanation of this position:

“Rationalists typically distrust our senses and believe that gaining knowledge is a matter of logically deducing true propositions from absolutely certain starting axioms. The foundational axioms are said to be known immediately or intuitively without the need of sensory experience or deductive inference. Such knowledge is called a priori knowledge (as opposed to a posteriori knowledge which is known on the basis of experience. Early rationalists often referred to such a priori knowledge as ‘innate ideas’ — ideas that are somehow ingrained in the minds of all people regardless of their individual experiences” [3].

As we saw in the previous post, for Descartes this was necessary because there could be no other foundation for our knowledge. All experiential knowledge can in principle be doubted, he says, and any beliefs which can even in principle be doubted cannot be held without absolute certainty. The only proposition which cannot even theoretically be doubted is “I exist,” and hence this must become the foundation of all further knowledge. Indeed, from this one premise alone, apart from any experiential knowledge, Descartes thinks he can establish the existence of God, and from there the reliability of sensory perception.

Following Descartes came the rationalists Spinoza and Leibniz. Both built comprehensive metaphysical systems from the ground up using rationalistic principles. Spinoza’s system reached the conclusion of substance monism: in the entirety of existence there is only one substance, which is infinite and is both God and Nature; and everything else that exists is merely a mode of the one infinite substance [4]. Leibniz’s system reached a nearly opposite conclusion: reality is ultimately made up of an infinite number of “monads,” which are simple, immaterial entities — indivisible substances — which cannot causally influence each other but each of which nevertheless somehow mirrors all the others [5].

Needless to say, many found the conclusions of these rationalistic systems quite far-fetched, if not absurd. And thus arose empiricism as an epistemological framework in reaction to the rationalism Descartes founded. In contrast to rationalism, the empiricists held generally that “all knowledge comes through the senses,” and that “there are no inborn structures of human understanding that precede and mediate our experience of the world” [6]. Here is again a concise explanation:

“Whereas the rationalist says that knowledge is gained primarily via reason rather than experience, empiricism takes the opposite approach and says that all knowledge arises from experience. The empiricist rejects the rationalist belief that some ideas are innate or knowable apart from experience” [7].

One of the early major empiricists was John Locke. Locke’s Second Treatise on Government was hugely influential on modern political thought — especially in the United States — but his major philosophical work was An Essay Concerning Human Understanding. He begins the Essay:

“Since it is the understanding that sets man above the rest of sensible beings, and gives him all the advantage and dominion, which he has over them; it is certainly a subject, even for its nobleness, worth our labor to inquire into. The understanding, like the eye, whilst it makes us see, and perceive all other things, takes no notice of itself; and it requires art and pains to set it at a distance, and make it its own object” [8].

Seeing the results of rationalism, Locke decides to take a step back and examine our “understanding” itself in order to determine how and what exactly it is able to know. He goes on to state his primary goal:

“This, therefore, being my purpose to inquire into the original, certainty, and extent of human knowledge; together with the grounds and degrees of belief, opinion, and assent . . . . It shall suffice to my present purpose, to consider the discerning faculties of man, as they are employed about the objects, which they have to do with; and I shall imagine that I have not wholly misemployed myself in the thoughts I shall have on this occasion, if, in this historical, plain method, I can give any account of the ways, whereby our understandings come to attain those notions of things we have, and can set down any measures of the certainty of our knowledge, or the grounds of those persuasions, which are to be found amongst men, so various, different, and wholly contradictory; and yet asserted somewhere or other with such assurance and confidence, that he that shall take a view of the opinions of mankind, observe their oppositions, and at the same time, consider the fondness, and devotion wherewith they are embraced; the resolution, and eagerness, wherewith they are maintained, may perhaps have reason to suspect, that either there is no such thing as truth at all; or that mankind has no sufficient means to attain certain knowledge of it” [9].

We can see in this quote some of the distress caused by the rationalist project, where each thinker arrives at wildly different conclusions, but maintains that these conclusions are absolutely certain. The remedy, says Locke, is to examine the faculty of human understanding itself. What is its origin, what knowledge can it achieve, and to what extent? In short, Locke thinks the rationalists have gone way beyond the actual abilities of the human mind in their theories; and so his own aim is to try to find some limits to human understanding, so that we do not stray into error by going beyond them.

He begins by noting that our minds have immediate conscious awareness which consists of various thoughts or feelings. He assigns to these thoughts the term ideas, and defines it thus:

“[The term ‘ideas’ stands for] whatsoever is the object of the understanding when a man thinks . . . whatever it is, which the mind can be employed about in thinking” [10].

We are all directly aware that we are thinking; and whatever the object of our thinking is, is an “idea.” So, given that we are aware of the presence of these ideas, we must next ask ourselves: what is their origin? Where did they come from? How do we have them?

Locke considers two distinct possibilities. The first is that these ideas are innate. This, as we’ve seen, was the position of Descartes and the rationalists. Locke describes it as follows:

“It is an established opinion amongst some men, that there are in the understanding certain innate principles; some primary notions . . . characters, as it were stamped upon the mind of man, which the soul receives in its very being; and brings into the world with it” [11].

Locke, however, rejects this view as false and unnecessary. The only reason, he suggests, that one would believe in such innate ideas, is in order to provide a foundation for certainty in knowledge. But innate ideas are not needed to provide such a foundation, and hence they should be rejected. He writes:

“It would be sufficient to convince unprejudiced readers of the falseness of this supposition, if I should only show . . . how men, barely by the use of their natural faculties, may attain to all the knowledge they have, without the help of any innate impressions; and may arrive at certainty, without any such original notions or principles” [12].

In other words, our ideas are not innate, but rather are attained by our own natural faculties, a posteriori. If we discover that we have eyes that can perceive color, what reason would we have to think that we were born with colors as innate ideas? Rather, if we know that we have eyes that can perceive color, we ought to conclude that our ideas of colors are acquired through the faculties of the eyes, and are not in us innately. So, he says, “no less unreasonable would it be to attribute several truths, to the impressions of nature, and innate characters, when we may observe in ourselves faculties, fit to attain as easy and certain knowledge of them, as if they were originally imprinted on the mind” [13].

Next, Locke decides to examine the case for innate ideas, and then respond to it. The primary argument, he suggests, in favor of innate ideas is that there are certain principles which are universally agreed upon by all mankind:

“There is nothing more commonly taken for granted, than that there are certain principles both speculative and practical (for they speak of both) universally agreed upon by all mankind; which therefore they argue, must needs be the constant impressions, which the souls of men receive in their first beings, and which they bring into the world, with, as necessarily and really as they do any of their inherent faculties” [14].

But Locke finds this argument weak on two fronts: first, he says, there aren’t actually any principles universally known/agreed upon by all mankind. And even if there were, such universal acknowledgement would not actually prove those principles innate, if any other means of causing universal acknowledgement can be discovered.

In defense of the first point, Locke considers the two principles most likely to hold universal human assent: the principle of identity (“whatever is, is“) and the principle of non-contradiction (“it is impossible for the same thing to be, and not to be“). These principles are the foundation of all thought and rationality; without them we could not reason at all. And yet, asserts Locke, “these propositions are so far from having an universal assent, that there are a great part of mankind, to whom they are not so much as known” [15]. To support this claim, he points to children and those with extreme intellectual disabilities:

“For, first, ’tis 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 a near 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 of 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” [16].

Here Locke contends that any idea or principle cannot be imprinted on the mind if it is not actually perceived by the mind. This follows from his definition of ideas mentioned earlier: an idea is whatever is the object of thought. But something could not possibly be the object of thought without being perceived. So if an idea is not perceived, it is not really imprinted on the mind and hence is not known innately. “No proposition,” he states, “can be said to be in the mind, which it never yet knew, which it was never yet conscious of” [17]. But it is rather clear, thinks Locke, that certain people are simply not aware of the principles which are usual candidates for being innate ideas. Young children, for instance, surely cannot be said to actually be conscious of either the principle of identity or of non-contradiction. Neither can those with extreme intellectual disabilities. These principles are known only to those with developed cognitive/rational functionality. As such, these principles cannot be said to be truly universally known by all mankind, and hence universal assent cannot serve as an argument for innate ideas.

Neither can it be, for Locke, that the mere capacity for knowing these principles is sufficient to qualify them as innate; for, in that case, every principle would have to be said to be innate, because man has the capacity to know every intelligible principle: “If the capacity of knowing be the natural impression contended for, all the truths a man ever comes to know, will, by this account, be, every one of them, innate” [18]. But no one thinks that all of our ideas are innate; only that a number of basic, fundamental or universal ones are.

Perhaps one might respond to Locke that innate ideas are universally assented to, not by all mankind qua mankind, but by all mankind that has come to the use of reason. Children and those with extreme intellectual disabilities might not perceive such principles, but surely all adults who have and use fully functioning, developed rational capacities do.

In reply, Locke contends that, if basic principles are universally assented to by all who come to the use of reason, this fact could mean one of two things: the first is that the principles are discovered automatically by the use of reason; the other is that the coming to the use of reason is the time at which one simultaneously comes to know basic principles. Locke rejects both. On the first view, if reason discovers the principles, then by definition they are not innate, but acquired. As regards the second view, Locke argues that the coming to the use of reason is actually not the exact moment when people come to know such principles; many children, he points out, come to use reason long before they are actually aware of the principles of identity and non-contradiction. But, furthermore, even if it were the case that the coming to the use of reason was the precise time at which the principles came to be known, this would not prove them innate. In support of this he says:

“For by what kind of logic will it appear, that any notion is originally by nature imprinted in the mind in its first constitution, because it comes first to be observed, and assented to, when a faculty of the mind, which has quite a distinct province, begins to exert itself?” [19].

Why would the fact that mankind comes to know such principles when it comes to the use of reason prove that those principles are innate? After all, the fact that people come to have ideas of colors as soon as they gain use of their eyes does not show that our ideas of colors are innate. This returns us to Locke’s original argument: if it can be shown that man has natural faculties which enable him to acquire knowledge of basic principles without them being innate, then we ought not think them innate.

Locke goes on to consider and respond to several other arguments in favor of innate principles, both speculative and practical. Up to this point, we have practically equated innate principles and innate ideas. But though related, they are significantly distinct; and it is on this distinction that Locke furthers his case.

As we’ve already said, ideas are whatever are the object of thought. Principles are likewise objects of thought, but they are in the form of a proposition. Thinking of the color red is thinking of an idea; whereas thinking of the principle of non-contradiction is thinking of a principle. Thus far, Locke has been arguing specifically against there being innate principles. Now he points out that principles cannot be innate unless there are innate ideas, for principles are composed of ideas. Ideas are “the parts, out of which those propositions are made” [20]. He writes:

“Since, if the ideas, which made up those truths, were not, it was impossible, that the propositions, made up of them, should be innate, or our knowledge of them be born with us. For if the ideas be not innate, there was a time, when the mind was without those principles; and then, they will not be innate, but be derived from some other original. For, where the ideas themselves are not, there can be no knowledge, no assent, no mental, or verbal propositions about them” [21].

Since principles are composed of ideas, if there were no innate ideas, there could be no innate principles. Innate ideas might not have to be temporally prior to principles, but they are at least logically prior; and the latter could not exist without the former. So are there innate ideas, apart from composite principles?

Locke thinks not. “If we will attentively consider newborn children, we shall have little reason, to think, that they bring many ideas into the world with them . . . . There is not the least appearance of any settled ideas at all in them; especially of ideas, answering the terms, which make up those universal propositions, that are esteemed innate principles” [22]. As he has pointed out earlier, if any principles are innate, surely the principles of identity and non-contradiction are. And yet, consider the ideas which compose these principles. For the principle of non-contradiction — it is impossible for the same thing to be, and not to be — is composed of several ideas such as impossibility and identity (at least implicitly in this principle, explicitly in the principle of identity). But how many young infants have a distinct understanding of these concepts? “For,” says Locke, “if those innate ideas, are not clear and distinct, so as to be universally known, and naturally agreed on, they cannot be the subjects of universal, and undoubted truths” [23].

But it is quite clear that newborn infants have many other ideas before coming to have such ideas of impossibility and identity. The first ideas infants have are those of hunger, thirst, warmth, pain, white and black and other colors, sweet and bitter, etc. These simple ideas are obviously present in us before all others. Indeed, explains Locke, it seems that many of our other ideas are actually derived from these basic ideas. The child first comes to have the idea of its mother, and then later the idea of some stranger; and only after having both these ideas can it entertain the idea of samenessdifference, and hence of identity. Locke gives an overview of this process:

“The senses at first let in particular ideas, and furnish the yet empty cabinet; and the mind by degrees growing familiar with some of them, they are lodged in the memory, and names got to them. Afterwards the mind proceeding farther, abstracts them, and by degrees learns the use of general names. In this manner the mind comes to be furnished with ideas and language, the materials about which to exercise its discursive faculty; and the use of reason becomes daily more visible, as these materials, that give it employment, increase” [24].

It seems quite obvious that an infant’s knowledge of ideas such as colors, pain, thirst, etc., is not innate but acquired. Children aren’t born already knowing colors; they learn colors from seeing them. From all of this Locke concludes that men do not have innate ideas imprinted on the mind, and hence neither do they have innate principles or any innate knowledge. We are born “empty cabinets,” or, in his own terminology which has become famous, we are born tabula rasa. Blank slates.

Locke’s rejection of innate knowledge was the inception of modern empiricism. If we are born blank slates, without any prior, innate knowledge, then all of our knowledge must be acquired from a source external to ourselves. Locke argues that this external source is experience, and in particular the senses. In the next post we will explore Locke’s theory of how precisely we acquire and accumulate knowledge, and the significant implications of this theory for the progression of modern philosophy.



This post is meant as a descriptive overview of the philosophical thought of John Locke. It is not meant to necessarily express or reflect my own philosophical views or beliefs. 

[1]. John Lawrence Hill. After the Natural Law: How the Classical Worldview Supports Our Modern Moral and Political Values. San Francisco: Ignatius Press, 2016. 129.

[2]. Ibid.

[3]. Steven B. Cowan and James S. Spiegel. The Love of Wisdom: A Christian Introduction to Philosophy. Nashville: B&H Publishing Group, 2009. 52.

[4]. Blake D. Dutton. “Benedict De Spinoza (1632—1677).” The Internet Encyclopedia of Philosophy. 

[5]. Douglas Burnham. “Gottfried Leibniz: Metaphysics.” The Internet Encyclopedia of Philosophy.

[6]. Hill. Natural Law. 134.

[7]. Cowan and Spiegel. The Love of Wisdom. 54.

[8]. John Locke. An Essay Concerning Human Understanding. Abridged and edited by Kenneth P. Winkler. Indianapolis: Hackett Publishing Company, 1996. 1.1.1

[9]. Ibid. 1.1.2

[10]. Ibid. 1.1.8

[11]. Ibid. 1.2.1

[12]. Ibid.

[13]. Ibid.

[14]. Ibid. 1.2.2

[15]. Ibid. 1.2.4

[16]. Ibid. 1.2.5

[17]. Ibid.

[18]. Ibid.

[19]. Ibid. 1.2.14

[20]. Ibid. 1.4.1

[21]. Ibid.

[22]. Ibid. 1.4.2

[23]. Ibid. 1.4.4

[24]. Ibid. 1.2.15







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