The principle of association, or of suggestion as it is termed by the more recent writers on the philosophy of the human mind, is the great and controlling law of the mental frame; it is that principle which enables us to supply all our wants, to adapt means to ends, to call up the knowledge of the past, to look into the undeveloped events of the future. It is this associating faculty which may be looked upon as truly the master workman of the mind. Its agency is requisite in the action of all our mental powers, and consequently in pointing out the intellectual differences between the sexes, it is proper never to lose sight of so important a modifier of mental character. Metaphysicians tell us that there are three principles or laws, according to which the association of ideas operates. 1st. Resemblance. 2d. Contiguity in time or place. And 3d. Contrast. Now if we examine into these three divisions, we shall find each one susceptible of a subdivision into two classes, marked and distinct. Thus 1st. There may be resemblance in the objects themselves. Or 2d. In the effects or emotions which they excite. For example, I see a man--he is like, in face and feature, to one I knew well in France--I think immediately of the Frenchman: here is resemblance in objects themselves. I see a violent hurricane--it reminds me of the desolating ravages of a Zenghis Khan, or Tamerlane: here is resemblance in the effects, and not in the objects themselves. I hear the cooing of the dove, and I think of the gentleness and innocence of the child. I hear a man reviling and blaspheming his God, and I think of midnight darkness: here is similarity in the emotions excited by the objects. A corresponding division may be made of contrast. Thus I see a dwarf, and he calls instantly to my mind the largest man I ever saw: this is contrast in the objects. I see a raging, destructive lion, and think immediately of the meek and humble Saviour of the world: here is contrast in the effects. I see the white and tender lily on the drooping stalk, and I think of the fiendish passions of a Macbeth or a Richard: here is contrast in the emotions excited by the objects. Lastly, contiguity in time and place may be divided into casual and fixed; thus I see a man today whom I saw yesterday in company with another: I instantly think of that other. I hear the last _eclipse_ mentioned, I think of the place I was in at that time, the company I was with, the anecdotes told, &c. In the first instance we have casual contiguity in place, and in the second in place and time both. I see the moon on the meridian, and think of the tides in our rivers. I see a magnet, and I think of its attraction for iron; here is necessary contiguity in time, and in the last instance in place too. Upon this last species of contiguity is dependent that most important of all relations, the relation of cause and effect, and of premises and conclusions.