The initial argument that Berkeley presents states that the only things that we can know are the things that we can perceive with our senses and/or reflect upon.  These things are immaterial.  Immaterial things can be perceived through any or all of the following methods: hearing, seeing, tasting, touching or smelling.  Characteristics or qualities that we can perceive immediately through our senses are known as secondary characteristics. We may argue that there are aspects or characteristics like extension or motion that go beyond these five senses.  However, Berkeley points out that these primary characteristics are reducible to any one of the secondary characteristics.  Material things, or matter, are things that we cannot perceive with our senses.  Because we cannot perceive them, we cannot know them, and because we cannot know them, we cannot reflect on them.  Therefore, because they are unknowable, they don’t exist.  To put this all another way – those things which are immaterial (perceivable) are mind dependent and those things which are material (not perceivable) are mind independent.  No thing exists that is not mind dependent, therefore mind independent, or material, things do not exist.

 Hylas brings up the question of what would happen if Philonous were annihilated.  Although it is presented as an argument, it serves as more of a question of clarification.  Is Philonous really so arrogant as to believe that the existence of all things depends upon any one person perceiving it, or is there some grand unifying perceiver?  Philonous responds with the statement that immaterial things do not depend upon him perceiving them, but that they are being perceived by something – and that something must at the bare minimum be God.  God is understood to be omni-benevolent, omniscient, omnipotent and omnipresent.  On these grounds, nothing could exist without him being aware of it, and therefore, because it couldn’t, it doesn’t.  This also provides the argument that not only do material things not exist, they can’t.  At least not as long as God is who we think He must be.

 Stemming from this point, Hylas brings up another argument in an attempt to take out Philonous’s immaterialistic claims by attacking what Philonous says God is in contrast with what he depicts Him as.  Philonous states that God is the cause of all things in nature, and His existence and continued perception of all creation is the only thing that keeps it around.  In a disturbing observation, Hylas raises the question of evil.  If God is the cause of everything, evil must also be pinned on Him.  This defies what has already been established about God’s character – namely omni-benevolence.  If this characteristic of God can be proved false, other aspects such as omniscience and omnipresence can possibly fall as well.  Without the omniscience and omnipresence of God, there is no “grand unifying perceiver”, and without this, there is no assurance that if we, the perceiver are annihilated, anything will continue to exist.  However, if it did (continue to exist), it would be mind dependent and therefore matter.  Such a thing destroys Philonous’s philosophy completely.
Philonous responds by saying that God did not create evil, but created the means for it to become a possibility.  It is because of him that it is possible to kill, but that does not mean that he is direct cause of it – he is simply the cause of the means.  It is we, as humans, who have taken (through Nature) the amoral things that God created and twisted them into evil.  He implies that although we exist because of and within God, we are not puppets.  His nature accommodates our will, and it is our will that causes evil.  The nature of God within Philonous’s immaterialism is defended and Philonous is safe on that front.

 Hylas doesn’t quite buy the concept the material things do not exist.  It sounds suspicious to him that just because a thing is mind independent it follows that it cannot exist.  One of his objections to Philonous comes in the form of the question that he (Hylas) is aware of ideas that he has that he could neither have produced on his own nor could they have produced themselves.  He claims that it would then follow that because they did not come from either from him or themselves, they must have come from matter.  To expound – in this argument, Hylas implies a trilemma.  All ideas that he has must have an origin that they are produced from.  The options are that he, himself, produced them, they produced themselves, or they were formed from a conglomeration of sensations and reflections on a pre-existing something-or-other.  He rules out the possibility that he could have produced them based on the preexisting supposition that we simply cannot create ideas and then rules out the possibility of these ideas producing themselves from nothing due to the fact that ideas are always either causes or effects and sometimes both, but never simply stand on their own.  The process of elimination leaves us with the third possibility standing.  Because it is neither number one nor number two, it must be number three.  This “pre-existing something-or-other” is what Hylas deems “matter.”

 Philonous’s response to this is simply to deny that what Hylas is referring to is matter.  He acknowledges that the argument is valid, but he doesn’t like the definition of one of the words in the conclusion.  He simply says that matter is inactive, and because something that is inactive cannot be a cause, matter is not what Hylas is referring to.  A point that he makes but Hylas fails to push him on is the concept of something inactive not being able to produce an effect.  Philonous’s very words are “How can something unthinking be a cause of thought?”  This point is very weak.  I see a chair in front of me – it’s not thinking (because, being a purely physical thing lacking any sort of mind, it is unable to do so), and yet I’m thinking about it.  Based on this counterexample alone, Philonous’s whole response to Hylas’s objection is nullified.  It is true that a non-thinking thing can be a cause of thought – if it wasn’t there and never was, we couldn’t think about it. 
 Sadly, the weakness of this point has very little observable effect on the overall argument.  It hints that Philonous may not have any idea what he’s talking about in this regard, but this does little to injure his opinion of the existence of matter.  The most this does is weaken his credibility, but it does not weaken the actual argument for immaterialism that he presents.

 We have failed to produce any evidence that might discredit the “Grand Unifying Perceiver” (who is the glue that holds the entire theory together) or prove that there are mind independent things.  Although chopping out either of these pillars could have completely destroyed immaterialism, neither approach proved possible.  It can be concluded, therefore, that due to a lack of any debilitating evidence, Berkeley (through Philonous) must be correct.