Berkeley on Material Substratum
During the last half of the First Dialogue, Hylas tries to recover from any slips that he might have made. One of his suggestions is the following:
On the one hand, sensible things may be viewed as sensations which are mind-dependent and which cannot exist in any unperceiving thing. On the other hand, sensible things may be viewed as so many modes and qualities which cannot be conceived to exist on their own (and which require that we suppose an unknown support or substratum).
I believe that this proposal is actually Hylas’ way of adopting a Lockean strategy of distinguishing between sensible qualities (as they are in us) and sensible qualities (as they are in the object). Recall that in the last discussion, I expressed concern that Philonous’ arguments against Hylas’ attempt to distinguish between sensible things in us and sensible things in the object assumed the “Equivocation Theory”. I worried that his response did not adequately address Locke’s position. I suspect that Hylas’ proposal (above) is intended as a Lockean way of drawing the distinction.
If I am right about this, then not only does Philonous argue against “material substratum” he also argues against Locke’s way of making sense of secondary qualities (as they are in the object and as they are in us). Thus, in addition to getting rid of material substratum, Philonous also closes off another escape route from his earlier argument (Pain/Pleasure and Perceptual Relativity). Recall that he was trying to convince Hylas that sensible qualities were mind-dependent (and so force Hylas into skepticism) as well as proving that it is incoherent to suppose that sensible qualities exist in (unperceiving) material substance. By attacking this (Lockean) way of distinguishing between sensible qualities as they are in us and as they are in the object, he is preventing Hylas from wiggling out of the arguments.
Philonous grants Hylas the following two claims: (1) The substratum is not sensible (only its modes and qualities are immediately perceivable); (2) There is no positive idea of what it is. NOTE: Philonous does NOT use these two claims AGAINST Hylas. Rather, he insists that at least Hylas must have “a relative notion” of substratum (i.e. he must at least understand the relation between the substratum and the accidents/qualities).
Philonous’ main argument is this. Either Hylas explains the relation by using spatial language (i.e. “support” “standing under” “spreading”) or Hylas has no way of explaining the relation at all.
Hylas explains that substratum is “spread under” the accidents. He also agrees that extension is JUST a mode or quality and that it is “somewhat entirely distinct” from the substratum. This means that substratum must be “spread under” extension as well. The problem, however, is that in order to be “spread under” the substratum must be extended. This requires a new quality of extension so that the substratum can support the first quality of extension. But in order to be “spread under” the new quality of extension, the substratum must be extended. There is an infinite regress.