Therefore it was, that though I began my first lecture by defining superstition, I did not begin my second by defining its antagonist, science. For the word "science" defines itself. It means simply knowledge; that is, of course, right knowledge, or such an approximation as can be obtained; knowledge of any natural object, its classification, its causes, its effects; or in plain English, what it is, how it came where it is, and what can be done with it. And scientific method, likewise, needs no definition; for it is simply the exercise of common sense. It is not a peculiar, unique, professional, or mysterious process of the understanding: but the same which all men employ, from the cradle to the grave, in forming correct conclusions. Every one who knows the philosophic writings of Mr. John Stuart Mill, will be familiar with this opinion. But to those who have no leisure to study him, I should recommend the reading of Professor Huxley's third lecture on the origin of species. In that he shows, with great logical skill, as well as with some humour, how the man who, on rising in the morning finds the parlour- window open, the spoons and teapot gone, the mark of a dirty hand on the window-sill, and that of a hob-nailed boot outside, and comes to the conclusion that someone has broken open the window, and stolen the plate, arrives at that hypothesis--for it is nothing more--by a long and complex train of inductions and deductions of just the same kind as those which, according to the Baconian philosophy, are to be used for investigating the deepest secrets of Nature. This is true, even of those sciences which involve long mathematical calculations. In fact, the stating of the problem to be solved is the most important element in the calculation; and that is so thoroughly a labour of common sense that an utterly uneducated mart may, and often does, state an abstruse problem clearly and correctly; seeing what ought to be proved, and perhaps how to prove it, though he may be unable to work the problem out for want of mathematical knowledge. But that mathematical knowledge is not--as all Cambridge men are surely aware--the result of any special gift. It is merely the development of those conceptions of form and number which every human being possesses; and any person of average intellect can make himself a fair mathematician if he will only pay continuous attention; in plain English, think enough about the subject.