When you said to your friend that there was a water fountain over there, the knowledge of real existence you expressed was of this third kind. As you looked at the fountain you knew that there was then something distinct from your mind really existing—the water fountain. Presumably you also knew many other things distinct from your mind to exist at that time: the floor you were standing on, the hallway you waited in, the doors in the hallway, etc. The knowledge you shared with your friend, however, concerned the existence of the water fountain.
You knew that the water fountain existed distinct from your mind. Locke gives a somewhat unusual name to knowledge of the external world. There is something special, according to Locke, about how knowledge of the external world is achieved that sets it apart from how knowledge of other matters, such as mathematical knowledge, is achieved. According to Locke, knowledge of the external world is different than what he calls intuitive knowledge.
Intuitive knowledge is knowledge that we grasp immediately and without any need for proof or explanation. For example, anyone who has ideas of the colors white and black and compares those ideas immediately knows that white is not black. This is the kind of knowledge we often have concerning the meanings of words, at least when words are given explicit definition.
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Locke also holds that knowledge of the external world is different than the kind of knowledge we achieve through proofs or argument. When someone proves that the sum of the three interior angles of a triangle is equal to the sum of two right angles through a proof with multiple steps, Locke calls such knowledge demonstrative knowledge. Locke would say that such a person has demonstrated their conclusion.
Knowledge of the external world is not arrived at by any such argument or proof. Knowledge of the external world is not achieved through thinking about the definitions of our terms or comparing ideas that we have already acquired.
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Instead, knowledge of the external world is achieved in sensory experience. It is through the entrance of an idea into our mind through the senses that we have knowledge of the external world. Suppose that the water fountain you saw was newly installed and had a fresh coat of crimson paint. As you looked at the water fountain and light reflected from the fountain to your eyes an idea of that distinct crimson color entered your mind. According to Locke, as the sensation of that color entered your mind you knew that something crimson existed distinct from your mind by its somehow producing that sensation in you.
Your knowledge of the existence of something crimson is therefore acquired in a way distinct from either intuitive or demonstrative knowledge. It does not depend on a proof or on comparing ideas already existing in your mind. Such knowledge is achieved upon looking at the water fountain and the water fountain's effect on your mind through your senses. So far, then, we have seen both the what and the how of knowledge of the external world according to Locke. What we know is real existence.
How we know it is through sensation—through the reception of ideas into our minds. The what and the how combine to place some severe limits on what Locke thinks we can know about the external world. First, our knowledge of the external world only extends as far as current sensory experience. As you look at the water fountain you know that it now exists.
When you look away from the water fountain as you turn back to your friend, you no longer know that it now exists. You only now know that it existed when you were looking at it. Similarly, you do not know that it existed before you looked at it. Locke does think that it is highly probable for you that the water fountain existed before and after you look at it.
Indeed, he thinks that it is nearly, if not completely, impossible for you to avoid believing that the fountain existed before you saw it and continues to exist after you turn away. Your belief that the water fountain exists when you are not looking at it, then, is both rational and psychologically compelling, according to Locke. Our knowledge extends over relatively little of the world we ordinarily believe to exist.
We only know to exist the sensible objects of our immediate sensory environment that are currently affecting us. Second, we only know the world as it appears to us through our senses. We do not know its underlying nature as it is in itself. This point can be helpfully illustrated by considering a new case. Suppose, for example, that you go on a field trip to gold country.
You and the rest of the class dip a sieve into the river and sift out a few flakes of a yellowish metal. The class then goes into a mine, chips off chunks of rock, crush them up, and sift out more pieces of yellowish metal from the crushed stone.
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At the end of the field trip the class spreads all of the collected pieces of yellowish metal in front of them. As you survey the spread of hunks of yellowish metal you can know that there now exist several distinct objects that affect your mind by producing certain ideas in it—sensations of yellow, solidity, etc. What you do not know is that there is some underlying nature that now exists in each of these hunks of stuff. Moreover, you do not know that they all have the same underlying nature.
We are ignorant, in other words, about both the underlying nature of each individual object as well as whether the objects that appear similarly to us have similar underlying natures. There may be tremendous evidence supporting the theory that describes the underlying microstructure of these hunks of stuff and even explains why a microstructure of that type produces the appearances you now see. Such microstructure or underlying nature, however, is not part of how the hunks of stuff now appear to you. Thus, while it may be overwhelmingly probable that some underlying common nature exists in all of the things spread before you, you do not know that that nature exists before you.
The belief that gold exists would be a very rational one to hold, based on all of the evidence we have to support our best physical and chemical theories. Nevertheless, such a belief would not be knowledge. Third, knowledge of the external world does not extend to other minds. Recall that Locke takes knowledge of the external world to be sensitive knowledge. Sensitive knowledge is achieved as a result of things operating on us through our senses. Locke does not think that other minds affect us directly through our senses.
Our own mind produces ideas in us through what Locke calls reflection, a kind of inner sense directed at our own mind. Those bodies then affect our minds through our senses. As a result, no other minds directly produce ideas in our minds through our senses. What : in particular instances of knowledge of the external world we know the existence of a thing external to our mind. When you saw the water fountain, for example, you knew that a crimson thing, that is a thing with a power to produce a certain sensation in you, then existed.
How: in particular instances of knowledge of the external world we know the existence of a thing with various powers to affect our mind by producing ideas in our mind by virtue of our awareness of the entrance of those ideas into our mind. When you saw the water fountain, for example, you knew that a thing produced a certain visual idea in your mind at that time; that a crimson sensation was then entering your mind.
In section 1 we explored what sensitive knowledge is : what do we know? The final Book of the Essay is dedicated to knowledge and opinion. Locke begins Book IV with a definition of knowledge. To appreciate the potential tension between the definition of knowledge and sensitive knowledge it is worth quoting the definition at length. Locke writes:.
Knowledge then seems to me to be nothing but the perception of the connection and agreement, or disagreement and repugnancy of any of our ideas. In this alone it consists. Where this perception is, there is knowledge, and where it is not, there, though we may fancy, guess, or believe, yet we always come short of knowledge. Locke and his readers frequently shorten this definition of knowledge by calling knowledge the perception of agreement of ideas.
This entry will adopt that convention. Foremost is how to resolve an ambiguity in the definition. Second, one may read the definition as stating that knowledge is the perception of agreement between ideas—the perception of agreement of one idea with another idea. As we will see below in section 2. In the margin next to the paragraph following the definition of knowledge, Locke noted in his personal copy of the Essay that knowledge is the perception of agreement between two ideas. To begin, one might wonder: what does an agreement between two ideas tell us about what exists beyond those ideas?
Knowledge of the external world, according to Locke, is knowledge of the existence of something distinct from our mind and so, of course, distinct from the ideas in our mind. Even Locke himself notes that the mere existence of an idea of something does not guarantee the existence of what that idea is an idea of. Merely having an idea of a freshly painted crimson water fountain does not guarantee that a freshly painted crimson water fountain really exists.
At this point, if there is to be any hope, we ought to take a step back and ask: what are the two ideas that agree in sensitive knowledge? It seems clear that if I know the crimson water fountain exists, my idea of it will be one of the ideas. What is the second idea? We might start making progress on this question by considering the content of sensitive knowledge. As detailed in section one above, we know that a thing exists distinct from our mind. For example, when you saw the freshly painted crimson water fountain down the hall, you knew that a crimson thing really exists.
Perhaps, then, sensitive knowledge involves the perception of agreement between the idea of a thing and the idea of real existence. When you look down the hall and know the water fountain exists you perceive an agreement between your idea of the crimson water fountain and the idea of real existence. The problem here can be made vivid by adopting a particular understanding of what it is for ideas to agree. In proving, for example, that the sum of the interior angles of a triangle is equal to the sum of two right angles, one perceives through a series of steps that the ideas are connected by the relation of equality.
But what would the connection between the idea of real existence and the idea of a thing, such as your idea of the freshly painted crimson water fountain, be?
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Again, contrast sensitive knowledge with intuitive knowledge of the meaning of a term. Any thing that is a yellow metal is yellow. What, then, is the connection between the ideas perceived to agree in sensitive knowledge and how is such a connection perceived through sensory experience? That is, it seems to make all knowledge depend on reflecting and comparing our ideas to one another in an attempt to understand relations between our ideas. But knowledge of the external world is patently not a priori.
Locke and Stillingfleet corresponded in a series of public letters. One of the very first criticisms Stillingfleet leveled at Locke was that his definition of knowledge in terms of ideas makes knowledge of the real world, including even knowledge of its existence, impossible.
Locke: Knowledge of the External World
This criticism persisted even into the twentieth century. Locke, such readers maintain, makes all knowledge a priori. Knowledge of the external world is not a priori. For now it is enough to recognize that Locke surely did not simply miss the apparent problem. That leaves us with the second option. Locke, on this view, brought out a tension with excruciating clarity but was not able to resolve it and instead merely wallowed in it clinging to both sources of the tension.
Though historical figures are as prone to error and clinging to positions they cannot adequately defend as any of us, it is generally best to explain such error or dogmatic clinging rather than simply leave it as unexplained brute failure. Locke, on these views, found himself caught between the expanding and improving new science, and its mechanistic world view, on the one hand, and an old epistemological paradigm with its emphasis on certainty, on the other.
To this end, Locke divides ideas into simple and complex ideas. Simple ideas are passively received by the mind and have no other ideas as parts. So, for example, when I bite into a pineapple I might receive several different simple ideas. One such idea would be the taste of the pineapple. Another might be the feeling of solidity or resistance as I bite into it.
Yet another might be the particular wet, slippery texture of the fruit in my mouth, etc.
The taste, the various textures, the different shades of yellow, all are different simple ideas for Locke. More specifically, these are all simple ideas of sensation; simple ideas produced in the mind by things outside of the mind operating on it through the senses. Locke also holds that we have simple ideas of reflection. They are ideas produced in the mind when those operations are active. All of these simple ideas of reflection and sensation are passively received by the mind. Complex ideas are ideas produced by the mind operating on ideas that are somehow already in the mind, whether simple or complex.
One way to form complex ideas is by putting two ideas together. Or, one might combine ideas of certain bodily movements corresponding to certain forms of music to make the idea of a dance. All of these would be complex ideas. The operations Locke most frequently discusses are operations of combining ideas, comparing ideas, and abstracting ideas. Sensation, reflection, and operations of the mind can explain all of the ideas human beings have according to Locke. That is, all of the contents of our thoughts can be traced to origins in sensation or reflection and some combination of mental operations.
Simple ideas of sensation are unique among all ideas in that they both represent the external world as well as represent their object perfectly. We can consider each of these features of simple ideas—that they represent external reality and that they represent it perfectly well—in comparison to other ideas. Simple ideas are produced in our minds by other things operating on us.
As a result, Locke claims, they represent the power to produce those ideas—that is, the object a simple idea perfectly represents is the power to produce that idea. Simple ideas are not the only ideas that represent mind-independent reality, however. Our ideas of things, whether particular individuals or kinds of things, also represent mind-independent reality.
Locke calls this type of idea ideas of substances and they are complex ideas. For example, my idea of a particular individual horse, Mr. Ed, is an idea of a substance. It is an idea of a particular thing which has various qualities. Ideas of substances are therefore ideas that represent or at least purport to represent extra-mental reality. We have other ideas besides simple ideas and ideas of substances, however. We also have ideas of relations and modes.
For reasons that go beyond the scope of this entry, Locke does not take our ideas of either kind to represent mind-independent reality. Simple ideas and ideas of substances alone among all ideas represent the external world. Though simple and substance ideas are alike in representing the external world, they differ with respect to how well they represent the world.
Only simple ideas, according to Locke, represent the external world perfectly. Whether an idea of a particular individual substance Mr. Ed or an idea of a kind of substance horses , our ideas of substances all fail to some degree in representing what they aim to represent. To see this difference, we can first consider why simple ideas represent their object perfectly.
According to Locke, simple ideas represent the power to produce those ideas in us. That is all they represent. Ideas of substances, by contrast, purport to represent an individual or kind of individual. To do so requires representing that individual or kind as having all and only the qualities it in fact has. If my idea of Mr. Ed does not include an idea of the color of his eyes, then my idea of Mr. Ed falls short of representing Mr. Ed as he really is. It is not, in Locke's terms, an adequate idea. Similarly, if my idea of Mr.
Ed represents him as having a dark spot above his tail, but Mr. Ed does not have such a spot, my idea is again an inadequate idea. Now, to have an adequate idea of a particular substance or kind of substance would be to represent not only all of its sensible qualities—that is, ideas of all of the ways in which it can affect our senses—but also to have ideas of all of its abilities to affect other things. At the very least, we simply cannot bring any given thing to interact with all of the other things in the universe to understand the effects it may have on them or them on it.
Simple ideas of sensation, then, stand alone as ideas that both represent the external world and perfectly represent it. For that reason it has seemed to some that simple ideas of sensation are fit to explain sensitive knowledge. Simple ideas have external content in the sense that they represent their cause. Such ideas are fit for knowledge of the external world because inferences from effects to causes is of sufficient reliability to count as knowledge.
Even if one grants this interpretation of the external content of simple ideas, there are different ways of filling in the details. How the details of this content are filled in, moreover, has implications for the content of sensitive knowledge. One possibility is that simple ideas are what M. The causes of that idea across different occasions may have nothing in common, and may bear no similarity to one another outside of their ability to produce that idea in your mind.
A second possibility is that simple ideas represent something like their normal or designated cause. It may be the cause that God has ordained for an idea. It may be the cause that most often produces the idea. It may be the cause that was naturally designed to produce the idea.
Which of these readings a proponent of this interpretation adopts is not especially important for the purposes of this entry. What is important is that what is meant by the power to produce an idea in this sense is a particular kind of structure in the world. To illustrate the difference between these interpretations consider the following comparison.
Take a particular sweet taste—say, the taste of the glaze on a donut—and a particular non-sweet taste—say, the taste of Tabasco hot sauce. Now consider the effects of the so-called Miracle Berry. If one eats a miracle berry, tabasco sauce will taste like donut glaze and donut glaze will taste like Tabasco sauce. Consider this sequence. On blank effect readings, powers to produce simple ideas are fully perceiver-relative entities.
As a result, the Tabasco sauce has two different powers at T0 and T2. At T0 it has the power to produce the idea of the taste of Tabasco. At T2, because of the effects of the miracle berry, it now has the power to produce the idea of the taste of donut glaze and no longer has the power to produce the idea of the taste of Tabasco. On this reading, the Tabasco sauce has the same powers at T0 and T2 because it has the same chemical structure and would have the same effect on a normal perceiver. Recent Locke scholars such as MR Ayers and Martha Bolton have paired externalism about the content of simple ideas with externalism about the knowledge such ideas allow for.
On the blank effects reading, if you judge that the cause of a simple idea exists on the basis of my having that simple idea, you cannot fail to be wrong. Such judgments are perfectly reliable and therefore ought to be regarded as knowledge. If you are blindfolded, unknowingly ingest a miracle berry, sample some Tobasco sauce and then judge that you have tasted some donut glaze you are, in a sense, correct and have sensitive knowledge.
You have tasted something with the power to produce the simple idea of the taste of donut glaze in you. That is all, on this view, the knowledge of the external world we have: there exist certain powers to affect our minds by producing ideas in us. On this reading we only know the world in relation to ourselves. On the stronger, more external readings, if you judge that the cause of a simple idea exists on the basis of having that simple idea, you are normally right.
If you are blindfolded, unknowingly ingest a miracle berry, sample some Tobasco sauce, and then judge that you tasted some donut glaze you are wrong and do not have sensitive knowledge. You have not sampled the usual cause of that idea. When you do, however, taste some actual donut glaze and on that basis judge that there is something with the power to produce the idea of the taste of donut glaze in you, you are right and do have knowledge.
This reading of Locke makes his view more similar to that of contemporary externalist epistemologies which deny that having knowledge entails that one knows that one has knowledge the so-called KK principle. The blank-effects reading, by contrast, remains compatible with knowing that one knows. Rather, doing so highlights how Locke has resources from his philosophy of mind and its account of the content of thought to supplement his official definition of knowledge with a kind of reliabilism about knowledge.
They attempt to make sense of sensitive knowledge as the perception of agreement between ideas by finding a connection between the idea of real existence and the idea of a sensible object, such as the water fountain from section one. Interpretations developed by Newman, Allen, and Nagel attempt to draw this connection through an idea of reflection.
Simple ideas of sensation are produced by objects external to our mind operating on us through our senses. The aforementioned interpreters claim that ideas of reflection function as a kind of cognitive faculty indicator analogous to something like a time stamp on a video or photograph.
Recording devices frequently time stamp what they record. That is, the recording produced by the device includes information about the time it was recorded. These interpretations attribute a similar view to Locke when it comes to the mental faculty by which an idea comes to be in the mind. The mind, in being aware of its activities, stamps any given idea with an idea of the faculty by which the former is produced in the mind on that occasion.
This cognitive faculty indicator provides the connection between the idea of the sensible object and the idea of real existence. According to Locke, a sensory experience of the sun is manifestly different from a memory of the sun. In fact, Locke claims that a sensory experience of the sun is as distinct from a memory of the sun as it is from a sensory experience or memory of the moon.
According to those like Allen, Nagel, and Newman, Locke explains this difference as a matter of each way of thinking about the sun involving distinct ideas of reflection. The idea of actual sensation is an idea of reflection; an idea of the mental faculty responsible for producing the idea of the sun in the mind at that time. Later that night when remembering how the sun looked at midday, an idea of the sun is again in the mind but this time it is stamped with the idea of memory.
The idea of memory is likewise an idea of reflection; an idea of the mental faculty active in producing the idea of the sun in my mind at this later time. According to this line of interpretation, there are three ideas involved in any given instance of sensitive knowledge. First, there is the idea of the sensible object—the idea of the sun or your idea of the water fountain. Second, there is the idea of sensation. This is an idea of reflection.
Third, there is the idea of real existence. The idea of sensation functions as an intermediary connecting the idea of the sensible object to the idea of real existence. The connection between the idea of sensation and the idea of real existence is supposed to be the kind of a priori connection involved in intuitive and demonstrative knowledge. If you are having a sensation then the cause of that sensation exists outside of your mind. Sensation just is being affected by the external world. Given that an idea is stamped with the reflective idea of sensation, then we can safely infer that the cause of the idea so-stamped exists outside of our mind.
The connection between the idea of sensation and the idea of the sensible object is not like this—and it is not clear exactly what this relation is according to Locke possibly co-occurrnce in the mind or some special mode of binding. The important point to note is just that the agreement between the idea of sensation and the idea of real existence is a different kind of agreement than that between the idea of sensation and the idea of the sensible object. Interpreters disagree on what to make of this difference in the relation between the three ideas involved in sensitive knowledge. Newman suggests that the relation between the idea of actual sensation and the idea of the sensible object the idea of the sun only yields a probable opinion and not strict knowledge.
Nagel and Allen, by contrast, hold that both the relation between the idea of actual sensation and the idea of the sensible object as well as the connection between the idea of actual sensation and the idea of real existence are knowledge conferring connections. In section 2. The journal continues its tradition of excellence today … Find out more. Latest articles Language Loss and Illocutionary Silencing. Autonomy and Aesthetic Engagement. Infinity, Causation, and Paradox , by Alexander Pruss. The Reduction of Necessity to Essence.
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