The object which we have chiefly in view at present is, to point out the great end designed by Nature in all these actions, which is simply _the application of knowledge_. There is the knowledge that objects entering the eye will give pain, and that the shutting of the eye will defend it. This we have shown is not an instinctive operation, but must have been acquired by experience;--and it is this principle, into the nature of which we are now enquiring, that prompted the child in the special case to apply its knowledge by shutting the eye. In like manner, in the case of the missile thrown at the head, there is a previous knowledge of the effect which it will produce, and a knowledge also of the means by which it is to be avoided,--and it is avoided;--and in the case of losing the equilibrium, there is nothing more than the application of a latent knowledge, now suddenly brought into use on the spur of the moment, that by the movement of the foot the body will be supported. The principle, whatever it be, which instigates children and adults to do all this, is the subject of our present enquiry, and which for the present we have denominated the "Animal," or "Common sense." We shall therefore a little more particularly attend to its various indications. The operation of this principle in the infant has already been pointed out. When it has learned by experience that its nurse is kind, it stretches forth its little hands, and desires to be with the nurse;--when in its first attempt at walking it experiences a fall, it applies this knowledge, by refusing again for some time to walk;--and when it burns its finger at the flame of the candle, the application of that knowledge induces it ever after to avoid both fire and flame. In after life the same principle continues to operate both independently of reason, and in conjunction with it. In encountering the air of a cold night, we, without reasoning on the matter, wrap ourselves closer in our cloak. When we turn a corner, and meet a sharp frosty wind, we lower the head to protect the uncovered face. When we emerge from the house, and perceive that the dulness of the day indicates rain, we almost instinctively return for a cloak or an umbrella. And the mariner at sunset, when he sees an opening in the sky indicating a storm, immediately takes in sail, and makes all snug for the night. In all these cases we perceive a principle within us, frequently operating along with reason, but sometimes also without it, which prompts us to apply our previous knowledge for our present comfort and advantage.[7] The constant operation of such a principle in our nature, no matter by what name it is called, leads us, as plainly as analogy and natural phenomena can do, to conclude, that it ought to be carefully studied, and assiduously cultivated in the young, during the period usually assigned for their education.