Astronomy is ... the only progressive Science which the ancient world produced.

Every failure is a step to success. Every detection of what is false directs us towards what is true: every trial exhausts some tempting form of error.

It is a test of true theories not only to account for but to predict phenomena.

Nobody since Newton has been able to use geometrical methods to the same extent for the like purposes; and as we read the Principia we feel as when we are in an ancient armoury where the weapons are of gigantic size; and as we look at them we marvel what manner of man he was who could use as a weapon what we can scarcely lift as a burden.

But with regard to the material world, we can at least go so far as this;-we can perceive that events are brought about, not by insulated interpositions of Divine power, exerted in each particular ease, but by the establishment of general laws.

The hypotheses which we accept ought to explain phenomena which we have observed. But they ought to do more than this; our hypotheses ought to foretell phenomena which have not yet been observed; ... because if the rule prevails, it includes all cases; and will determine them all, if we can only calculate its real consequences. Hence it will predict the results of new combinations, as well as explain the appearances which have occurred in old ones. And that it does this with certainty and correctness, is one mode in which the hypothesis is to be verified as right and useful.

The hypotheses we accept ought to explain phenomena which we have observed. But they ought to do more than this: our hypotheses ought to foretell phenomena which have not yet been observed.