solely because we understand the nature of space, and therefore also the conditions of perspective involved in the perception of what is spatial. It is, therefore, needless to make the assertion 'Two lines appear convergent' intelligible by converting the verb 'appears' into a substantive, viz. an 'appearance', and then making the assertion relate to an 'appearance'. For--apart from the fact that this would not achieve the desired end, since no suitable predicate could be found for the appearance--the assertion that the lines _look_ or _appear_ convergent is perfectly intelligible in itself, though not capable of being stated in terms of anything else.[19] If we generalize this result, we may say that the distinction between appearance and reality, drawn with regard to the primary qualities of bodies, throughout presupposes the reality of space, and is made possible, and indeed necessary, by the nature of space itself. [17] Cf., however, p. 87 and pp. 89-91. [18] This is, of course, not refuted by the reminder that we see with two eyes, and that these are in different places. [19] It is important to notice that the proper formula to express what is loosely called 'an appearance' is 'A looks or appears B', and that this cannot be analysed into anything more simple and, in particular, into a statement about 'appearances'. Even in the case of looking at the candle, there is no need to speak of two 'appearances' or 'images'. Before we discover the truth, the proper assertion is 'The body which we perceive looks as if it were two candles', and, after we discover the truth, the proper assertion is 'The candle looks as if it were in two places'.