Like many of the 17th Century philosophers such as Descartes, and Leibniz, Locke’s work on Substance and Essence were very much a reaction against Aristotelian Scholasticism and the idea of substantial forms. The mould in which something was created is its substantial form, according to Aristotle, and it owes its characteristics to it. A stone then was created after the mould of stoniness and owed its weight to its nature, which tried to return to the earth, which came of its substantial form.
Locke, however, rejected classical doctrine as unscientific, preferring nstead to work on a system of classification which reflected the true nature of objects. As Ayers said, ‘the foundations of our system of classification… are not universal forms or moulds but objective resemblance’s between things. Locke then wished to classify genera on the basis of a resemblance between their primary qualities. Locke takes the already used word ‘essence’ and calls a thing’s ‘real essence’ “the very being of a thing, whereby it is what it is” (3. 3. 15) or later on as “The real constitution of things from which all their properties flow”.
By this Locke is referring to the micro-structural arrangement of parts or ‘corpuscular structure’ measurable in primary terms which give an object its observable visible secondary qualities. This real essence, Locke believes, is what is responsible for the properties of objects. There is a problem however with this definition of ‘real essence’ as a replacement for a scholastic substantial form. As an object’s micro- structural arrangement is undetectable, and Locke agrees with this, how is it possible for us to recognise and therefore classify groups of objects, species or genera?
Lock’s answer is his notion of nominal essences. Locke believed that in observing any given substance the “combination of simple ideas that we believe belong” to that whole substance. Locke defines simple ideas elsewhere as the basic irreducible concepts we have that will build up our more complex ideas. For example, the complex concept of a ‘Zebra’ would be made up of many ideas such as ‘black’, ‘white’, and ‘horse’. Some of these such as ‘horse’ could still be broken down further but others will be simple like ‘black’.
So as Ayers describes it, “A nominal definition onsists of a non-explanatory list of attributes peculiar to the species and is so suitable as a criteria for recognition”. So though the nominal essence of a substance could be used to classify groups and must be observed to make distinctions, it is the ‘real essence’ reflects the true nature of an object and contains its explanatory power. As Lowe said “we now have two notions of essence, one explanatory and the other classificatory”. This is a move by Locke away from the scholastic idea that substantial form could play both roles.
Locke disagreed that nominal essence had much credence as it did not inform s as of the characteristics that are inseparable from the substance and truly make it what it is. If we consider Gold and whether anything that is ‘nominally’ identical to Gold, if possible, could be called Gold. Obviously Locke’s answer would be no, in order to be like Gold it must have its identical ‘real essential nature’. Putman answer – division of linguistic labour theory Contemporary philosophers have raised problems with Locke’s idea of ‘real essential natures’.
Dewey (in Copi) for example claimed that a substance’s essential nature is determined purely by the vocabulary we use and that the ords trick us into thinking there is more to an object’s essential nature than our verbal concept of it. Dewey gives the example of a table, saying that if I change its colour this is purely accidental and therefore the table remains the same whether green or brown. What if, he speculates, it is brown tables only which interest me? Then a change in colour would reflect an essential change in the table for me.
Therefore “the very being of the thing, whereby it is what it is” would be contingent only on the vocabulary used to describe it and any quality could be described as an ssential characteristic. Exploring this further causes yet another problem for Locke. If his distinction is consists in separating the explanatory from the classificatory then according to Locke it is the ‘real essence’ alone which causes the object to be as it is. Now if an object’s appearance changes, it would cease to be as it was and would begin to display different properties. Though the change seems nominal, isn’t this an essential change.
As Copi says, “If all properties depend upon its real essence then every change is an essential one. ” Even time can be seen as hange and then it would be completely impossible to speak of a thing’s real essence. Further criticism came from Berkeley and Hume, fellow empiricists, who seized on the idea of real essence as completely unknowable and decried it as un-empiricist and ultimately unprovable. Locke’s defence has come from modern science. Scientists now study the micro-structural composition of objects and determine what Locke would consider to be an object’s ‘real essence’. This also weakens Dewey’s objections.
By specifying the micro-structural criteria for real essence, e recognise when a substantial change occurs. Brownness, or greenness, as characteristics are secondary qualities and are only definable in terms of primary qualities, which are verifiable and quantitative. It would be a mistake then to try and attribute these subjective, indefinable qualities to an object’s real essence. Locke’s discussion of real and nominal essences, attempting to move away from scholastic doctrine, was definitely a step forward. As many of Locke’s ideas are in agreement with modern science it is clear the distinction deserves merit.