C. S. Lewis. The Discarded Image. An Introduction to Medieval and Renaissance Literature. Cambridge University Press. 1964.

pp. 14-15:

In every period the Model of the Universe which is accepted by the great thinkers helps to provide what we may call a backcloth for the arts. But this backcloth is highly selective. It takes over from the total Model only what is intelligible to a layman and only what makes some appeal to imagination and emotion. Thus our own backcloth contains plenty of Freud and little of Einstein. The medieval backcloth contains the order and influences of the planets, but not much about epicycles and eccentrics. Nor does the backcloth always respond very quickly to great changes in the scientific and philosophical level.

Furthermore, and apart from actual omissions in the backcloth version of the Model, there will usually be a difference of another kind. We may call it a difference of status. The great masters do not take any Model quite so seriously as the rest of us. They know that it is, after all, only a model, possibly replaceable.

The business of the natural philosopher is to construct theories which will ‘save appearances’. Most of us first meet this expression in Paradise Lost (viii, 82) and most of us perhaps originally misunderstood it. Milton is translating σώζειν τὰ φαινόμενα, first used, so far as we know, by Simplicius in his commentary on the Aristotelian De Caelo. A scientific theory must ‘save’ or ‘preserve’ the appearances, the phenomena, it deals with, in the sense of getting them all in, doing justice to them. Thus, for example, your phenomena are luminous points in the night sky which exhibit such and such movements in relation to one another and in relation to an observer at a particular point, or various chosen points, on the surface of the Earth. Your astronomical theory will be a supposal such that, if it were true, the apparent motions from the point or points of observation would be those you have actually observed. The theory will then have ‘got in’ or ‘saved’ the appearances.

pp. 16-18:

On the highest level, then, the Model was recognised as provisional. What we should like to know is how far down the intellectual scale this cautious view extended. In our age I think it would be fair to say that the ease with which a scientific theory assumes the dignity and rigidity of fact varies inversely with the individual’s scientific education. In discussion with wholly uneducated audiences I have sometimes found matter which real scientists would regard as highly speculative more firmly believed than many things within our real knowledge; the popular imago of the Cave Man ranked as hard fact, and the life of Caesar or Napoleon as doubtful rumour. We must not, however, hastily assume that the situation was quite the same in the Middle Ages. The mass media which have in our time created a popular scientism, a caricature of the true sciences, did not then exist. The ignorant were more aware of their ignorance then than now. Yet I get the impression that when the poets use motives from the Model, they are not aware, as Aquinas was, of its modest epistemological status. I do not mean that they have raised the question he raises and answered it differently. More probably it has never been before their minds. They would have felt that the responsibility for their cosmological, or for their historical or religious, beliefs rested on others. It was enough for them that they were following good auctours, great clerks, ‘thise olde wise’.

Not only epistemologically but also emotionally the Model probably meant less to the great thinkers than to the poets. This, I believe, must be so in all ages. Quasireligious responses to the hypostatised abstraction Life are to be sought in Shaw or Wells or in a highly poetical philosopher such as Bergson, not in the papers and lectures of biologists. Delight in the Medieval Model is expressed by Dante or Jean de Meung rather than by Albertus and Aquinas. Partly, no doubt, this is because expression, of whatever emotion, is not the business of philosophers. But I suspect this is not the whole story. It is not in the nature of things that great thinkers should take much interest in Models. They have more difficult and more controversial matters in hand. Every Model is a construct of answered questions. The expert is engaged either in raising new questions or in giving new answers to old ones. When he is doing the first, the old, agreed Model is of no interest to him; when he is doing the second, he is beginning an operation which will finally destroy the old Model altogether.