Abstract

1. The spatial perception requirementCassam surveys arguments for what he calls the ‘Spatial Perception Requirement’ . This is the following principle: " SPR: In order to perceive that something is the case and thereby to know that it is the case one must be capable of spatial perception. " A couple of preliminary glosses. By ‘spatial perception’ Cassam means either perception of location, or perception of specifically spatial properties of an object, such as its size and shape. Second, Cassam takes it that there is something basic about cases in which one's perceiving that something is the case depends on perception of an object. That is, he takes it that there is something basic about such cases as that in which, for example, you perceive that the door is open by perceiving the door.On this second point, it is not quite obvious that one could not perceive that things are thus and so if one could not perceive material objects. Cannot someone lost in fog, for example, perceive that it is foggy, even if they cannot see a thing because of the fog? Moreover, suppose we have someone who cannot perceive that things are thus and so. This person has only a series of sensations. Is it obvious that this person could not come to have knowledge of their world by reasoning about the probable causes of those sensations? These points seem to me to have some interest, but I will not pursue them here. I will assume we are considering cases in which propositional knowledge is grounded in perception that such and such is the case, and that this in turn depends on perception of objects.One sort of argument you might give for SPR runs as follows. Perception of an object demands that you have perceptually differentiated the object from its …