reality in standard philosophical usage, how things actually are, in contrast with their mere appearance. Appearance has to do with how things seem to a particular perceiver or group of perceivers. Reality is sometimes said to be twoway-independent of appearance. This means that appearance does not determine reality. First, no matter how much agreement there is, based on appearance, about the nature of reality, it is always conceivable that reality differs from appearance. Secondly, appearances are in no way required for reality: reality can outstrip the range of all investigations that we are in a position to make. It may be that reality always brings with it the possibility of appearances, in the counterfactual sense that if there were observers suitably situated, then if conditions were not conducive to error, they would have experiences of such-and-such a kind. But the truth of such a counterfactual seems to be grounded in the facts of reality. Phenomenalism holds, to the contrary, that the facts of reality can be explained by such counterfactuals, but phenomenalists have failed to produce adequate non-circular analyses. The concept of reality on which it is two-wayindependent of experience is sometimes called objective reality. However, Descartes used this phrase differently, to effect a contrast with formal or actual reality. He held that there must be at least as much reality in the efficient and total cause of an effect as in the effect itself, and applied this principle as follows: ‘There must be at least as much actual or formal reality in the efficient and total cause of an idea as objective reality in the idea itself.’ The objective reality of an idea seems to have to do with its having representational content, while actual or formal reality has to do with existence independent of the mind. Thus the quoted principle relates features of the cause of an idea to the representational content of the idea. Descartes’s main intended applications were to God and material objects. See also DESCARTES. G.Fo.