Idealism vs. Materialism Berkeley does provide an instrumentally better theory, if you are referring to defeating skepticism, as he recognizes and fixes a major issue with Locke’s theory. The difference between Berkeley and Locke’s theories are their views on primary and secondary qualities. Locke’s theory includes a distinction between primary and secondary qualities, as he asserted that primary qualities were mind-independent, and that secondary qualities were mind-dependent. Berkeley disagrees with Locke’s distinction, and asserts that both primary and secondary qualities are mind-dependent for several reasons. The first being that just as secondary qualities vary according to the state of the viewer’s senses, Berkeley states that so can primary qualities. Color, a secondary quality, can be said to differ depending upon the circumstances in which it is being looked at, for example if you put a white bed under a green beam, then the bed would appear green instead of the white that it would be seen as in other scenarios. In this same way, Berkeley gives the example of a primary quality, extension, and how it can vary depending upon the vantage point of the person who is observing it. If one is very far away, that person would consider the item as looking very small, whereas if the same person was closer to the object, they would state the opposite about the item.
Another reason that Berkeley gives for disagreeing with Locke is that the two classes of qualities, primary and secondary, are intertwined and cannot be separated. Berkeley (1710) puts this claim well saying, “In short, extension, figure, and motion, abstracted from all other qualities, are inconceivable. Where therefore the other sensible qualities are, there must these be also, to wit, in the mind and nowhere else.” (p.14) One could not imagine a colorless strawberry or feel a textureless banana, therefore, to assert that primary qualities such as extension, solidity, and number could exist externally without secondary qualities also being present are preposterous in Berkeley’s opinion. Berkeley designates both primary and secondary qualities as ideas, and asserts that ideas can only be like other ideas, that is only existing in the mind and not externally. Through this new classification of primary qualities, Berkeley fixes Locke’s logical discrepancy and presents an instrumentally better theory than Locke.
Berkeley’s view originates from the same empiricism that Locke’s does, but he does not rely on the same arguments he uses to refute Locke. Locke’s view is affected by these worries due to his inaction in taking his arguments to their furthest claims. Locke embraced empiricism, which is the theory that all knowledge is derived from sense-experience, yet Locke still thought of external objects as something whose existence could be known. The problem with this view, that Berkeley goes after, is that, if you cannot use any of the five human senses to detect matter, as those are mind-dependent secondary qualities, and you cannot use primary qualities to detect material objects, as Berkeley showed that those are also mind-dependent, then why would an empiricist believe anything exists? Considering that in the empiricist view the only way they believe knowledge is derived is through their senses, if they cannot obtain any sense-data about external objects, then they have no viable reasons to believe in these objects’ existence.
Berkeley’s attack on abstract objects does put a lot of pressure on materialism, as materialism relies heavily on human’s ability of abstraction and the stipulation that material objects are mind-independent. These are both claims that Berkeley attacks heavily. Though I will concede that Berkeley offers some persuasive arguments against materialism, I would claim that an exploration of the objections to idealism leads to the conclusion that Berkeley’s attack on materialism is not enough to utterly undermine it. Berkeley’s views as a whole overcomes Locke’s, but Berkeley’s overall argument faces powerful issues such as allusions to solipsism, his failure to show that objects are mental because they are known, and his misconception of the contradiction of perceived unperceived items are all major concerns for his argument as whole. Due to all of these issues I would claim that Berkeley’s argument is not sound and therefore does not undermine materialism.