From Rationalism to Empiricism
Rationalism vs. Empiricism Empiricism: All knowledge ultimately rests upon sense experience. All justification (our reasons for thinking our beliefs are true) ultimately relies upon information from sense experience. Seeing is believing. Rationalism: Not all knowledge ultimately rests upon sense experience. At least some of our beliefs can be justified without any appeal to information from sense experience. E.g., 2+2=4.
Descartes, Locke, Berkeley Descartes is a rationalist. Descartes believes that the reliability of our senses can only be established by a process of reasoning that is itself independent of what we might know through sense experience. Locke and Berkeley are both empiricists. Both believe that everything we know must ultimately stem from sense experience, i.e., from our sensations.
From Descartes to Locke What do we directly know in sense experience?
Hey, Descartes, Whadayaknow?
What I really knew vs. what I thought I I know that I exist. knew I know that I am a thinking thing, a mind. i.e., the subject of conscious experiences. I know I have ideas or sensations in my mind. These mental contents are what I directly or immediately perceive. But I have simply assumed that my ideas come from things outside me, and that they resemble those things in all respects.
Descartes: (What he says in 3 rd Med.) What we directly or immediately know in sense experience is merely an idea or sensation that exists in our minds. In hallucination, these ideas do not (correctly) resemble any external object. In perception (as opposed to hallucination) they do.
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Sensations vs. Material Objects According to Descartes, ideas or sensations exist only in our minds, and they are what we immediately or directly know in sense experience. Material objects ( real things ) exist outside our minds. They are not what we immediately experience. Rather, they are the causes of what we immediately experience (i.e., of the ideas in our minds).
Sensations vs. Material Objects Mind Idea Object in mind in world
Descartes, Locke, Berkeley Locke and Berkeley agree with Descartes that we directly perceive only ideas or sensations, which exist only in the mind. Locke agrees with Descartes that there is a world of objects that exists independently of our ideas and sensations. Descartes argues that there is such a world outside our minds. Locke simply assumes there is such a real world. Berkeley disagrees with Descartes and Locke about a world that exists independently of mind. Berkeley claims that objects are merely collections of ideas.
John Locke Ideas vs. Qualities Primary Qualities vs. Secondary Qualities
Ideas vs. Qualities
John Locke Whatsoever the mind perceives in itself, or is the immediate object of perception, thought, or understanding, that I call idea; and the power to produce any idea in our mind, I call quality of the [thing] wherein that power is. [Paragraph 8]
Locke s Causal Theory of Perception: Idea: Whatsoever the mind perceives in itself the immediate object of perception. Quality: The power [in an object] to produce any ideas in our mind.
Ideas vs. Qualities Ideas: Exist in our minds. They are the sensations we are directly aware of. Qualities: Exist in objects that exist outside of our minds. They are the properties in the objects that cause us to have various kinds of sensations.
Qualities (in objects) cause ideas (in our minds) Mind Idea Object in mind in world Our ideas (of objects) include ideas of these qualities. Objects have qualities that cause the ideas we have of them.
Welcome to Reality! Real objects (objects that exist whether we perceive them or not) Have all sorts of properties Also know as qualities Such as their shape, size, weight, color, temperature, etc. These are qualities in the objects.
We have ideas of objects These objects (by reflecting light waves, etc.) cause various sorts of ideas or sensations to exist in our minds. So, the quality of shape (in the object) causes our idea or sensation of shape. Likewise, the quality of color (in the object) causes our idea or sensation of color.
Primary vs. Secondary Qualities
Primary and Secondary Locke divides the qualities (Qualities, remember, are qualities of objects.) into two kinds: Primary qualities: Such as size, shape, weight, location, etc.; and Secondary qualities: Such as colors, sounds, tastes, smells and temperatures (i.e., amounts of warmth or coolness).
What Locke says: the ideas of primary qualities of bodies are resemblances of [bodies], and their patterns do really exist in the objects themselves but the ideas produced in us by secondary qualities have no resemblance of them at at all. There is nothing like our ideas existing in the bodies themselves. [Paragraph # 15]
The Crucial Difference Some qualities of objects cause ideas in us where these ideas actually resemble the qualities in the object. These are primary qualities. Some qualities of objects cause idea in us where the ideas do not resemble the qualities in the object. These are secondary qualities.
Do the ideas in our mind resemble the qualities in the objects that caused these ideas in our minds? Mind s Eye Idea Object Does this resemble this?
Locke s Answer Only sometimes. Our ideas of primary qualities resemble those qualities in the object that caused us to have these ideas. Our ideas of secondary qualities do not resemble those qualities in the object that us to have those ideas.
Explaining the difference
Why don t our ideas always resemble their causes? Remember, we are explaining the sensations that we actually have. We explain things by understanding that how things really are explains how they actually appear. But this means that sometimes how things really are is not how they actually appear. The qualities of an object that don t actually appear the way our explanation say they really are are known as secondary qualities.
Paragraph 11 The next question to be considered is, how bodies produce ideas in us; and that is manifestly by impulse By impulse here, Locke is suggesting that objects impel particles that interact with our sense organs. This is the physics of his day. Today, we would say that objects reflect wavelengths of light, rather than that they emit particles.
Paragraph 12 If.. external objects be not united to our minds when they produce ideas [in us] it is evident that some motion must be thence continued by our nerves by some parts of our bodies, to the brains there to produce in our minds the particular ideas we have of them.
So, Objects outside our minds cause sensations in our minds. Different properties of objects cause different kinds of sensations. Science hypothesizes the properties objects must really have to explain the ideas we have of them. So, scientific explanations distinguish between how things really are, and how they appear to us. That is, they try to explain what properties things must really have in order to explain the experiences that we of them.
Welcome to the Atomic Cafe
A brief introduction to Atoms Atoms weren t simply discovered by investigation. They were first hypothesized. The atomic theory (which goes back to the Greeks) attempts to explain the properties that big things have in terms of basic properties of the smaller parts (atoms) of which it is actually composed.
Greek Atomism Everything in the natural world is composed of different collections of the same basic atoms. So, paper, rocks, trees, human bodies, etc., are all composed of the same basic smallest pieces, or atoms. These atoms have basic or fundamental properties. Atomism explains the properties of big things (collections of atoms) in terms of these fundamental properties of small things (the atoms out of which big things are composed.)
Reducibility Big things are, in the end, nothing but collections of small things (of atoms.) The properties of big things are thus explained in terms of (or reduced to ) the basic properties of the small things (atoms) out of which they are composed. Example: being a table. A collection of atoms is a table because of the arrangement and basic properties of the atoms out of which it is composed.
So, Properties of big things are explained in terms of (i.e., are reducible to) the fundamental qualities of the smallest ultimate particles of which they are composed. We can call these fundamental qualities of the smallest ultimate particles their primary (or original ) qualities.
Locke What Locke calls Primary Qualities are just these fundamental properties of the basic particles out of which everything is composed. These are the fundamental properties that things have. All other properties (like that of being a table) must be explained in terms of (must be reducible to) these primary qualities. Any atomic explanation will distinguish fundamental (primary) from non-fundamental (non-primary) properties.
Locke s Secondary Qualities Locke lists: color, sound, taste, smell, feel, and warmth/coolness. These are (like the property of being a table) real properties that objects have. They are powers in objects to produce ideas in us. But (like the property of being a table), they aren t ultimate. The are reducible to the primary qualities of insensible particles.
First Difference Locke s Primary qualities of objects are the ultimate properties of the basic particles out of which things are composed. Locke s Secondary qualities of objects (like all real qualities that aren t ultimate properties of the basic particles) are reducible to the primary qualities of these particles.
Second Difference Locke s Primary qualities of objects cause ideas in our minds that resemble those qualities. Locke s Secondary qualities of objects cause ideas in our minds that do not resemble those qualities.
Summing Up According to atomism, all non-fundamental properties of objects are explained in terms of (are reducible to) the fundamental or primary properties of its smallest particles. And, for Locke, the ideas caused in us by primary qualities resemble those ideas, and he calls secondary qualities those qualities in objects (which are reducible to primary qualities) that cause ideas in us that do not resemble those qualities in the objects.
True Colors?
Back to Locke Locke says our ideas of primary qualities are resemblances of them. i.e., an object s primary qualities cause ideas in us that resemble those very qualities. Locke says our ideas of secondary qualities do not. i.e., an object s secondary qualities cause ideas in us that do not resemble those qualities in the object that caused us to have those ideas.
Its Not Easy Being Blue So, being blue (a secondary quality) is a property an object has because it has the power to cause certain kinds of ideas in our minds. It has this power because of the primary qualities of the particles out of which it is composed, and how these particles interact with our bodies in sense perception.
Being Blue So the blueness of a blue chair is real but not an ultimate or primary quality of the chair. The blueness of the chair is explained in terms of the fundamental properties of the particles out of which it is composed. We call the chair blue because the ultimate particles it is made out of reflect certain wave lengths of light, which in turn cause certain sorts of sensations to exist in our minds.
Where did Blue go? Which is blue? The sensation (idea) in our mind, or The quality (power) in the object? Blue is a quality of objects. Sensations aren t blue, any more than they are heavy! Sensations are of blue.
Stop me if you ve heard this one.
Falling Trees You ve all heard this one: If a tree falls in the forest with no one there to hear it, does it make any sound? How do you think Locke would answer this question. What does science tell you? Hint: The correct answer is: Yes and No.
Answer The tree in the forest disturbs air waves whether or not there is anyone there to hear it. (This is realism. ) But if no one is present, it doesn t produce any auditory sensations in anyone s mind. The confusion: We use the word sound both to talk about airwaves and to talk about sensations. But these are different things. Airwaves come from qualities (which exist outside our minds), while sensations are ideas that exist only in our minds.