Moreover, the fact that the inner speech of deaf signers consists of signs rather than sounds follows from the assumption that inner language is based on learned outer language.
But given that inner speech depends on having outer speech, acquired in a communicative situation, we are inclined to think that if anything is a by-product (or “spandrel”) here, it is inner speech.
The two-dimensional intension of S is true at (V, W) iff D epistemically necessitates that D' metaphysically necessitates S, where D is a canonical description of the scenario V and D' is a canonical description of the world W. If we understand epistemic necessitation in terms of a priori material conditionals and metaphysical necessitation in terms of subjunctive conditionals, this will be the case iff 'D ⊃ (D' => S)' is a priori, where the outer conditional is material and the inner conditional is subjunctive.
This is the most coarse-grained conception of content - the outer limit on a conception of content that meets the minimal conditions that we are requiring that any conception of representational content meet.
Speaking in popular and unphilosophical terms, we may say that the content of a thought is supposed to be something in your head when you think the thought, while the object is usually something in the outer world.
It is held that knowledge of the outer world is constituted by the relation to the object, while the fact that knowledge is different from what it knows is due to the fact that knowledge comes by way of contents.
The difficulty of this view is in regard to sensation, where it seems as if we came into direct contact with the outer world.
As a natural result of this state of affairs, it has come to be thought that the public senses give us knowledge of the outer world, while the private senses only give us knowledge as to our own bodies.
Our spontaneous, unsophisticated beliefs, whether as to ourselves or as to the outer world, are always extremely rash and very liable to error.
Thus, although it may be difficult to determine what exactly is sensation in any given experience, it is clear that there is sensation, unless, like Leibniz, we deny all action of the outer world upon us.