If space has only three dimensions we should expect all mankind to be aware of the fact, as they are aware of it.

But in the case of congruence, mankind agree in an arbitrary interpretation of sense-awareness when there is nothing in nature to guide it.
I look on it as no slight recommendation of the theory of nature which I am expounding to you that it gives a solution of this difficulty by pointing out the factor in nature which issues in the preeminence of one congruence relation over the indefinite herd of other such relations.
The reason for this result is that nature is no longer confined within space at an instant.

Space and time are now interconnected; and this peculiar factor of time which is so immediately distinguished among the deliverances of our sense-awareness, relates itself to one particular congruence relation in space.
Congruence is a particular example of the fundamental fact of recognition.

In perception we recognise.

This recognition does not merely concern the comparison of a factor of nature posited by memory with a factor posited by immediate sense-awareness.