Locke also distinguishes between the truly existing primary qualities of bodies, like shape, motion and the arrangement of minute particles, and the secondary qualities that are "powers to produce various sensations in us" such as "red" and "sweet." These secondary qualities, Locke claims, are dependent on the primary qualities.
He also offers a theory of personal identity, offering a largely psychological criterion.
It matters now that Mens Fancies are, 'tis the Knowledge of Things that is only to be priz'd; 'tis this alone gives a Value to our Reasonings, and Preference to one Man's Knowledge over another's, that is of Things as they really are, and of Dreams and Fancies." In the last chapter of the book, Locke introduces the major classification of sciences into physics, semiotics, and ethics.
Many of Locke's views were sharply criticized by rationalists and empiricists alike.
Substances are “nothing but the assumption of an unknown support for a group of qualities that produce simple ideas in us”.
Despite his explanation, the existence of substances is still questionable as they cannot necessarily be “perceived” by themselves and can only be sensed through the qualities.Substance is what holds qualities together while qualities themselves allow us to perceive and identify objects.A substance consists of ‘bare particulars’ and does not have properties in themselves except the ability to support qualities.Book I of the Essay is Locke's attempt to refute the rationalist notion of innate ideas.Book II sets out Locke's theory of ideas, including his distinction between passively acquired simple ideas, such as "red," "sweet," "round," etc., and actively built complex ideas, such as numbers, causes and effects, abstract ideas, ideas of substances, identity, and diversity.An Essay Concerning Human Understanding is a work by John Locke concerning the foundation of human knowledge and understanding.It first appeared in 1689 (although dated 1690) with the printed title An Essay Concerning Humane Understanding.Furthermore, Book II is also a systematic argument for the existence of an intelligent being: "Thus, from the consideration of ourselves, and what we infallibly find in our own constitutions, our reason leads us to the knowledge of this certain and evident truth, that there is an eternal, most powerful, and most knowing being; which whether any one will please to call God, it matters not! Locke connects words to the ideas they signify, claiming that man is unique in being able to frame sounds into distinct words and to signify ideas by those words, and then that these words are built into language.Chapter ten in this book focuses on "Abuse of Words." Here, Locke criticizes metaphysicians for making up new words that have no clear meaning.In anticipating a counter-argument, namely the use of reason to comprehend already existent innate ideas, Locke states, "by this means there will be no Difference between the Maxims of the Mathematicians, and Theorems they deduce from them: All must equally allow’d innate, they being all Discoveries made by the use of reason." Whereas Book I is intended to reject the doctrine of innate ideas proposed by Descartes and the rationalists, Book II explains that every idea is derived from experience either by sensation – direct sensory information – or reflection – "the perception of the operations of our own mind within us, as it is employed about the ideas it has got".In Book II, Locke focuses on the ideas of “substances” and “qualities”, in which substances are “an unknown support of qualities” and qualities have the “power to produce ideas in our mind”.