Variation--Constancy--Influence of Temperament--Of Observation--Bulls--Want of Knowledge--Effects of Emotion--Unity of the Sense of the Ludicrous. As every face in the world is different, so no two minds are exactly similar, although there is great uniformity in the perceptions of the senses and still more in our primary innate ideas. The variety lies in the one case, in the finer lines and expressions of the countenance, and in the other in those delicate shades and combinations of feeling which are influenced more or less by memory, reflection, imagination, by experience, education and temperament, by taste, morality, and religion. It was no doubt the view of this great diversity of thought that led Quintilian to say that "the topics from which jests may be elicited are not less numerous than those from which thoughts may be derived!" Herbert writes to the same purpose-- "All things are full of jest; nothing that's plain But may be witty, if thou hast the vein." But we are not in the vein except sometimes, and under peculiar circumstances, so that, practically, few sayings are humorous. It is more difficult to assert that there are any jests which would be appreciated by all. The statement that "some phases of life must stir humour in any man of sanity," is probably too wide. There is little of this universality in the ludicrous, but we shall have some reason for thinking that there is a certain constancy in the mental feeling which awakens it. It is also fixed with regard to each individual. If we had sufficient knowledge, we could predict exactly whether a man would be amused at a certain story, and we sometimes say "Tell that to Mr. ---- it will amuse him." But if his nature were not so disposed, no exertions on his part or ours could make him enjoy it. The ludicrous is dependent upon feelings or circumstances, but not upon the will. It is peculiarly involuntary as those know who have tried to smother a laugh. The utmost advance we can make towards making ourselves mirthful is by changing our circumstances. It is said that if a man were to look at people dancing with his ears stopped, the figures moving without accompaniment would seem ludicrous to him, but his merriment would not be great because he would know the strangeness he observed was not real but caused by his own intentional act. We may say that for a thing to appear ludicrous to a man which does not seem so at present, he must change the character of his mind.