Part, therefore, of these objections to our theory may, I think, be met by admitting that _some_ of the ... sensible qualities which we perceive do not exist at the places where they appear to exist, though ethers do. But there is, I think, another class of cases, in which we may be justified in denying that two things which (it is asserted) cannot occupy the same space, really cannot. I will take an instance which is, I think, typical. When we look at a drop of blood with the naked eye, we perceive a small red spot, uniformly red all over. But when (as we say) we look at the _same_ object under a microscope of a certain power, I am informed that we see a much larger spot, of similar shape, indeed, but _not_ uniformly red--having, in fact, small red spots at different positions in a yellowish field. And if we were again to look at the _same_ object through a microscope of much higher power still, we might perceive yet a third different arrangement of colours. Is there any fatal objection to supposing that all _three_ appearances--the uniform red spot, the yellowish field with reddish spots in it, and the third, whatever that may be--do all really occupy the same real spatial area? I cannot see that there is. We are familiar with the idea that a given spatial area may contain parts which are invisible to us. And hence, I think it is quite conceivable that parts of a given area may be _really_ occupied by one colour, while the whole is _really_ occupied by another. And this, I think, is what we actually _do_ believe in many cases. At all events, we certainly believe that the area which appears to be occupied by one colour really is _the same area_ as that which appears to be occupied by another. And, unless we assume that the area, in both cases, really is the same, we can certainly have no reason to deny that each colour does really occupy the area which it appears to occupy.