Dawn asked:

In the arguments which take place between Philonous and Hylas in the first of the Three Dialogues
Between Hylas and Philonous,Can Hylas' notion of material substance be defended against
Philonous' criticisms?

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The first thing we must take into consideration is the fact that in the actual dialogue, Berkeley has
biased the entire argument in favour of Philonous, in order to support his notion that the existence of
matter cannot be proved. Berkeley's constant concern was for the fate of common-sense beliefs and
religious truths , in an age when scepticism, atheism, and doubts about religion overall were coming
into the ascendancy of intellectualism. He believed that they could all be refuted together, and that
the key to their common refutation lay in the rejection of matter as a real entity. To achieve his
objectives Berkeley had to show that there is no material substance 'out there.' To know our own
ideas is to have a perfectly evident and sure grasp upon the real world ; that of sensible things or
ideas of sense. To show that the world of sensible bodies is a world of mind-dependent ideas, based
ultimately upon the infinite spirit, thus the grounds of atheism are removed.

In the dialogue, Philonous is enabled to push the objective beyond the attempts of Hylas to refute the
argument. For most of the argument Hylas is confined to agreeing with Philonous. There are some
attempts to make a case for 'external objects,' but they lack conviction and are easily shown to be
untenable by Philonous. Having made positive affirmation aboutmatter,Hylas finds himself struggling
with the burden of proof laid on him. The notion that material substance can be known as a supporter
of qualities, is easily disposed of by his rival. To hold that ordinary secondary qualities have only a
subjective reality, is to concede the point that they exist only in ideas, orobjects-in-perception.All that
remains is to show that there is no essential difference between primary and secondary qualities.
Hence the former must be considered just as mind — dependent as the latter.

Hylas' best course would have been to offer a direct rebuttal of the argument, as Kant actually did.
Kant claimed that Berkeley's immaterialism destroys the objective world. He alleged that Berkeley
reduces material things to subjective states and eventually to sheer illusion.

Hume also made Berkeley struggle to overcome his objection that, if the existence of ideas is one
with their being perceived, then the sensible world ceases to exist whenever the acts of perception
themselves cease. This would lead to a doctrine of intermittent existence and a consequent denial of
the permanence of sense things. The criticism forced Berkeley to appeal to the distinction between
God's mind and our own. Sensible things depend essentially and constantly upon the divine mind,
which always actually wills and perceives them. If Hylas had used Hume's argument then Philonous
would have been made to struggle, in so much that he would have to find proof , first for the existence
of God, and second to confirm that the divine mind was structured and functioned in the way claimed
by Berkeley.

John Brandon