Besides accepting the psychological analysis of Locke, Berkeley also adopts without question the assumption common to Locke and all the philosophers of the Enlightenment,――the assumption of the independence of the individual soul. “But besides all the endless variety of ideas or objects of knowledge, there is likewise something that knows or perceives them――what I call mind, spirit, soul, or self. By which I do not denote any one of my ideas, but a thing entirely distinct from them, wherein they exist, or, which is the same thing, whereby they are perceived.” Berkeley, therefore, (1) agrees with Locke that all knowledge is derived from sense-perception, _i. e._ he agrees with Locke’s empirical psychology, and (2) he also agrees with one of Locke’s assumptions, viz., that the spiritual substances exist. =The Negative Side of Berkeley’s Philosophy.= We have now pointed out Berkeley’s general relation to Locke and Hume, and more in particular his agreements with Locke. We are now prepared to examine the teaching of Berkeley by itself. Berkeley was obliged to devote a good deal of time to the negative side of his philosophy. Just as Locke could not construct an empirical psychology until he had disclaimed all allegiance to innate ideas, so Berkeley could not construct an idealism until he had brought to bear in a polemical fashion all his forces against abstract ideas. Of his two masterpieces he devotes the entire essay on the _Theory of Vision_ and a good part of his _Principles of Human Nature_ to this end. 1. In proof of this he advances his analysis of abstract ideas. He not only denies that abstract ideas have a corresponding external reality, but he even denies that abstract ideas exist in the mind itself. The deception in abstract ideas arises from the use of words as general terms. Words are always general; ideas are always particular. There is never an idea that exactly corresponds to a word. Words are useful not as a conveyance of ideas, but for inciting men to action and arousing the passions. Whenever a word is used, what we think of is the particular sense, idea, or group of sense objects that give rise to it. For example, the word “yellow” cannot be employed by us except in connection with the thought of some particular yellow thing. Berkeley is a nominalist of the extremest type.