So far we have considered higher animals: a dog, a cat, a horse. Let us now take a lower animal - a snail for example. We know nothing about its inner life, but we may be sure that its perception is very different from ours. In all probability a snail's sensations of its surroundings are very vague. It probably feels warmth, cold, light, darkness, hunger, and instinctively (i.e. incited by the pleasure-pain guidance) it crawls towards the uneaten edge of the leaf it sits on and draws away from a dead leaf. Its movements are governed by pleasure-pain; it always advances towards the one and retreats from the other. It always moves on one line - from the unpleasant towards the pleasant. And, in all probability, it knows and senses nothing except this line. This line constitutes the whole of its world. All the sensations entering from outside are sensed by the snail on this line of its motion. And these come to it out of time - from potentiality they become actuality.
For a snail the whole of our universe exists in the future and the past, i.e. in time. Only one line exists in the present; all the rest lies in time.
It is more than probable that a snail is not aware of its own movements; making efforts with its whole body it moves forward towards the fresh edge of the leaf, but it seems to it that the leaf moves towards it, coming into being at that moment, appearing out of time, as the morning appears to us.
A snail is a one-dimensional being.
Higher animals - a dog, a cat, a horse - are two-dimensional beings. To them space appears as a surface, a plane. Everything outside this plane lies for them in time.
Thus we see that a higher animal - a two-dimensional being as compared to a one-dimensional — extracts one more dimension out of time.
The world of a snail has one dimension - our second and third dimensions lie for it in time.
The world of a dog has two dimensions - our third dimension lies for it in time.
An animal may remember all the 'phenomena' it has observed, i.e. all the properties of three-dimensional bodies it has come into contact with, but it cannot know that that which for it is a recurring phenomenon is in reality a permanent property of a three-dimensional body - an angle, or curvature, or convexity.
This is the psychology of the perception of the world by a two-dimensional being.
For it a new sun will rise every day. Yesterday's sun has gone and will never recur again. Tomorrow's sun does not yet exist.