We do not, in fact, “observe” what it is here said that we observe; all this is _inferred_. What we observe, in astronomy, is a two-dimensional pattern of points of light, with a few bright surfaces of measurable size when seen through the telescope (the planets), and of course the larger bright surfaces that we call the sun and moon. Most of this pattern (the fixed stars) rotates round the earth once in every twenty-three hours and fifty-six minutes. The sun rotates in varying periods, which average twenty-four hours and never departs very far from the average. The moon and planets have apparent motions which are more irregular. These are the _observed_ facts. There is no logical impossibility about the formulæ doctrine of spheres rotating round the earth, one for each planet and one for the stars. The modern doctrines are simpler, but not one whit more in accordance with observed facts; it is our passion for _simple_ laws that has made us adopt them. The last sentence of the above quotation raises some further points of interest. “Rightly or wrongly”, the writer says, “we naturally conceive of these as having been so constituted and so maintained by some Force or Forces.” I do not deny this. It is “natural”, and it is “right or wrong”--more specifically, it is wrong. “Force” is part of our love of explanations. Everyone knows about the Hindu who thought that the world does not fall because it is supported by an elephant, and the elephant does not fall because it is supported by a tortoise. When his European interlocutor said “But how about the tortoise?” he replied that he was tired of metaphysics and wanted to change the subject. “Force”, as an explanation, is no better than the elephant and the tortoise. It is an attempt to get at the “why” of natural processes, not only at the “how”. What we observe, to a limited extent, is what happens, and we can arrive at laws according to which observable things happen, but we cannot arrive at a reason for the laws. If we invent a reason, it needs a reason in its turn, and so on. “Force” is a rationalising of natural processes, but a fruitless one since “force” would have to be rationalised also.