John Locke’s ‘Essay concerning Human Understanding’ (last edition 1705) is widely held to be one of the most significant philosophical works in the history of ideas. Regarded by most as the first British empiricist, Locke sought to explain and understand what we can know, or how knowledge of the physical world is achieved. His fundamental premise was that information is acquired through the senses (sensation) in the form of simple ideas, and is then reflected upon using the power of reason, simple ideas that are in agreement with each other thus produce knowledge. Such a proposition was revolutionary at the time of publication, as the accepted doctrine regarded knowledge as planted in the human mind at birth by God. Locke’s philosophy directly challenged this belief by using the distinction of primary and secondary qualities to show what it is possible to know of the physical world around us. Such a distinction (also used by Boyle and Descartes) relied upon a corpuscular theory and was argued by Locke as an explanation of how our senses provide us with knowledge – an argument that ultimately led to the rejection of innate ideas. One of the main criticisms of Locke’s theory arises from the idea of indirect representation, as he challenges what we really can know of our physical reality. Locke’s explanation of the substratum (the thing in which qualities are contained by) is also a point of contention for philosophers as it is considered largely indefensible.
It is the intention of this essay to demonstrate how Locke’s notion of primary and secondary qualities significantly contributed to epistemology, science and metaphysics. Furthermore, I intend to argue that the distinction between the primary and secondary qualities is one of major ontological importance and had the effect of changing the way that we could, and can, know the world.
Locke’s Essay was written at a time when Aristotle’s philosophy had been the accepted doctrine for two thousand years. Scholastic philosophy had purported to ‘know’ the world through reason based on certain premises. This naive empiricist philosophy asserted for example, ‘the earth is the centre of the universe’, and ‘women are naturally inferior to men’, and argued that an essence of an object was the quality that made something the type of thing it was – the essence of man is rational thought, the essence of a knife is its ability to cut. In Locke’s time however, these premises were wearing thin, a new mechanistic perspective that was based on prediction and observation, was being implemented by individuals such as Galileo and Newton. Using the principle of cause and effect, Locke examined knowledge and reduced it to its smallest component – the simple idea. The idea of yellow for example, is a simple idea. Locke advanced however, that only some of our ideas of objects correctly represent how they actually are. Our (complex) ideas of a yellow plant-pot for example are ideas of yellow, solidity, mass, stillness (as opposed to motion) and shape. Of these ideas says Locke, only stillness, shape and mass, are ideas that correctly represent the yellow plant-pot. The ideas of yellow and solidity are not intrinsic properties of the plant-pot, the yellow is only apparent when light is present, and if we put the plant-pot under a microscope then we see it is not solid. The things that cause us to have ideas of yellow, solidity, mass, stillness and shape of a yellow plant-pot are (according to Locke) the powers of the primary and secondary qualities of it. The powers of these qualities give us simple ideas which we combine (through reflection, or reason) to produce a complex idea i.e. the ‘yellow plant-pot. However Locke maintains that only the powers of primary objects (the mathematical qualities of mass, figure, motion or rest) are actual properties of the object. The powers of secondary qualities are reliant on the primary qualities – we think of sugar as having a sweet taste, yet it is only because of the shape and arrangement of its insensible particles, that we perceive the idea of sweet. In using this idea of corpuscularianism; (originally Boyle’s) that all things in the world observed in the world can be explained in terms of the arrangement (or composition) and motion of their smallest undividable part, Locke was asserting a very different theory of perception than his predecessors. The implications of his theory meant that we perceive the world in terms of causation; our ideas are the result of the operation of insensible particles on our senses. This idea was quite different in comparison to Aristotle’s elements explanation, which argued that; in perceiving an object, our senses become like the object (which is made up of a combination of the four elements, earth, fire, air and water). Although similar in some ways, Locke’s theory stood apart from Aristotle’s because his theory separated the qualities of objects in terms of what we perceive and what is actually there. Unlike Aristotle, who argued that what the senses perceive is what is actually present in the world, Locke’s theory accounted for the discrepancies in the senses. Though essentially his theory pointed out that the senses were capable of misleading us, it also made clear what it was possible to know of the physical world. And also how we become aware of this information, as it was a causal theory of perception. It also contrasted both Descartes’ and Plato’s belief in innate ideas. By laying down a method of perception and demonstrating that everything we know, we perceive from the senses, Locke was rejecting the notion that we are born with innate knowledge of the world. If we are born with a blank slate – tabular rasa upon which through the senses we gather information and knowledge of the world, then (unlike Descartes) we are born without knowledge of God. As his theory ruled out innate knowledge of God, it also opened the gate for atheism, as even Locke himself a type of Christian, was forced to accept that religious faith that does not rely on experience and reason,
“is only a ground for private, individual religious belief, which would be morally and intellectually wrong to make enforceable universally by the authority of the Church or the state” (E.J. Lowe p9 1995) .
During the 1600’s Britain the authority of the Church was the controlling force in dictating what we knew (by way of adopting scholastic philosophy) and many argue that Locke’s theory played a part in the type of culture we now have, as the idea God is not such a central fundamental focus for people as it was in Locke’s time.
In distinguishing between the primary and secondary qualities of objects, Locke was making an ontological distinction. The primary qualities, which are in the object, are mind-independent qualities and need no perceiver for them to exist. Whereas the secondary qualities which are a result of the primary qualities and not in objects, are mind-dependant, and rely on the relationship between the object and it’s perceiver. The famous example of whether a tree makes a sound when it falls in the woods when nobody is around to hear it, demonstrates that in the absence of a perceiver, the vibrations caused in the air by the tree falling, are not converted into an experience of sound, so sound is a secondary quality of the primary quality of motion and mass and is thus dependent on the human being there to hear it. Thus secondary qualities are relational qualities that only exist between the human perceiver and the object. This was an important point for Locke to make which raised several epistemological questions about (if his account is correct) how can we have actual knowledge of the world when everything we perceive through the senses is only apparent to us because of the arrangement and motion of particles (primary qualities) producing the powers of secondary qualities. If we perceive everything in terms of this then our ideas of colour, sound, taste and appearance only exist with us, and not in the physical world.
Thus in actual fact, when we are in the act of perceiving the world, we are really only perceiving our ideas of the world, we see an indirect representation of it. This idea creates a gap between the perceiver and the perceived, as the ideas we have of the physical world are not at all representative of what is actually present. Locke demonstrated this with his example of crushing an almond;
“Pound an almond, and the clear white colour will be altered into a dirty one, and the sweet taste into an oily one. What real alteration can the beating of the pestle make in any body, but an alteration of the texture of it?” (Locke Bk II VIII :20 1689)
The corpuscular composition has changed, and consequently, so have the ideas of the powers the secondary qualities produce; yet nothing has been added or taken away. Our senses are therefore incorrect when they inform us of the colour and taste of the almond, as when crushing it we are only changing the shape, which is apparent to us. This was an important scientific explanation that demonstrated that it is necessary that in order to have true knowledge of the world, we must rely upon the observable primary qualities of objects.
What was also important was that Locke was propounding the idea that knowledge cannot be achieved by philosophy alone. As in his time philosophy purported to explain the world in terms of premises that were directly (and they thought, correctly) observable by the senses. By distinguishing between the disciplines of science and philosophy (at that time they were interchangeable) Locke was ascribing to philosophy the chiefly critical function that it has today. Science observes the mathematical properties of objects and in applying a mechanistic perspective provides far more accurate predictions than philosophy was able to. The difference in trajectories, predicted by Galileo and Aristotle of the cannon ball is demonstrative of this idea, as Galileo’s mathematical calculations (based on the primary qualities) were far more accurate that Aristotle’s predictions based on (false) sensory input from the powers of secondary qualities.
One of several contentions that have remained with us of Locke’s theory, is his idea that something ‘though we know not what’ (Locke BK II XIII: 3 1689) supports the primary and secondary qualities – in Locke’s terms the substratum. The idea that the qualities of every object in the world are supported by something called the substratum that is unable to exist by itself, and does not have any qualities itself and only exists in relationship with the qualities of objects. However it is impossible (at least in Locke’s day) to understand how the qualities of a normal yellow lemon, could exist in the lemon, without something (i.e. the substratum) to hold them together. This assumption of the notion of the substratum however is arguably defensible if we relate it to the technology of Locke’s time. As it was impossible to know anything much about the inner workings of objects such as their corpuscular relationship, Locke, by the very logic of his theory was forced to give some explanation of what the qualities of objects inhere in. He is not able ‘to know what’, it is, that supports these qualities as technology is not able yet to inform him.
In using a scientifically based causal theory of perception, John Locke arguably made a great and far-reaching contribution to the areas of epistemology, science and metaphysics. By making the distinction between the primary and secondary qualities of objects and explaining the method of cause and effect in perception he clearly defined what, and how, it is possible to know of our physical world. Thus essentially dictating the role of science as the necessary enquirer into the physical world.
By demonstrating that the senses were unreliable only of some qualities, but not the mathematical mind –independent qualities he provided a clear and correct distinction between what we can know (and thus scientifically observe) and what we cannot.
Yet the idea that we perceive the world indirectly by only perceiving our ideas is a difficult pill to swallow. It does seem the one part of his theory, which does not correctly explain perception
Nevertheless his distinction of the qualities and his explanation of perception appear to correctly define how we receive information of objects. In Locke’s rejection of innate ideas he has a firm and sound basis on which to adhere this to – in his causal theory of perception. Unlike Descartes and Plato’s belief in innate knowledge, Locke’s theory can be observed and explained, and whether or not it is correct, appears a far better explanation than that of Plato, or Descartes.
In terms of historical significance, Locke’s theory by the very fact that it was revolutionary, and opposed some of the major beliefs of his time, was, and still is one of the major contributions towards the history of ideas and was one of the first empiricist texts that influenced our mechanistic view of the world that we now have
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