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Let us consider what we understand, and what we ought to understand, by the word "Science." The word itself is simply the Latin word Seientia, stripped of its Roman toga and put into an English dress. Its original meaning is "knowledge," and the Romans used it in its widest sense, as including all manner of facts and propositions which were known or supposed to be known. But in later times its meaning has been restricted. The domains of art and of literature have been struck out from the domain of science. In our modern view science deals with principles, art with practice. Science enquires about the laws of matter and mind, art applies these laws in the production of results. To ascertain the laws of animal life and of inherited qualities in science; to improve the breed of sheep and cattle by the application of this knowledge is art. But the domain of science is still very wide, and is further broken up by modern analysis into such sections as "pure science," dealing with abstract ideas; "physical science," investigating nature mathematically; and "natural science," studying the laws of life. Yet there is another analysis which requires to be made, and which seldom is made by those who speak of sciences in a popular manner. Science, we say, means "knowledge:" but what do we understand by "knowledge?" Under cover of this word are commonly confounded two very different states of mind, and the confusion has led to many serious results.

If we say that we know there is light in this room, and that we know the light is produced by the gas, we are speaking of two quite different kinds of knowledge, only one of which has any right in a strict sense to be called knowledge at all. The other is not knowledge but belief.

We know that there is light in this room; but we do not know that it is produced by burning gas; we only believe that it is.

Mark the difference. Knowledge is that of which the mind has direct perception. Belief is that state which the mind arrives at from the balancing of evidence.

That there is light here is not a matter of inference, or judgment, or opinion; it is net a conviction arrived at from weighing evidence; it is the simple perception of a sensation. There can be no possibility of denying it. It is true knowledge.

But to say that the light is produced by gas is to refer to a judgment—not a direct perception, We do not perceive the gas. It is far away from us. We argue in our minds "what produces this light? Is it the sun? Is it the moon? Is it candles? Is it gas?" We consider, and balance the evidence, and conclude that the probability of its being gas far outweighs all other suggestions. A conviction or belief is the result. But this is not true knowledge, and it has nothing like the certainty of true knowledge.

We never can be sure that all possible evidence, upon any subject whatever, has come before us; nor that we have equally and impartially weighed all the evidence we had. How do we know, for instance, that the gas-company are not trying an experiment to-night, and using something which is not gas after all? We mas have had the firmest belief that the light was produced by gas and yet find that we were wrong.

Every belief is open to contradiction, and liable to change. As long as a real belief exists at all it has the same force with us as if it were