If we imagine that a person enjoys a thing, that will be a sufficient reason for making us love the thing and desiring to enjoy it. If we imagine that a person enjoys a thing which only one can possess, we do all we can to prevent his possessing it. His enjoyment of the thing is an obstacle to our joy, and we endeavor to bring into existence everything which we imagine conduces to joy, and to remove or destroy everything opposed to it, or which we imagine conduces to sorrow. We see, therefore, that the nature of man is generally constituted so as to pity those who are in adversity and envy those who are in prosperity, and he envies with a hatred which is the greater in proportion as he loves what he imagines another possesses. We see also that from the same property of human nature from which it follows that men pity one another it also follows that they are envious and ambitious. If we will consult experience, we shall find that she teaches the same doctrine, especially if we consider the first years of our life. For we find that children, because their body is, as it were, continually in equilibrium, laugh and cry merely because they see others do the same; whatever else they see others do they immediately wish to imitate; everything which they think is pleasing to other people they want. And the reason is, as we have said, that the images of things are the modifications themselves of the human body, or the ways in which it is modified by external causes and disposed to this or that action. II If we imagine that we are hated by another without having given him any cause for it, we shall hate him in return. If we imagine that we have given just cause for the hatred, we shall then be affected with shame. This, however, rarely happens; we endeavor to affirm everything, both concerning ourselves and concerning the beloved object which we imagine will affect us or the object with joy, and, on the contrary, we endeavor to deny everything that will affect either it or ourselves with sorrow. This reciprocity of hatred may also arise from the fact that hatred is followed by an attempt to bring evil upon him who is hated. If, therefore, we imagine that we are hated by any one else, we shall imagine him as the cause of some evil or sorrow, and thus we shall be affected with sorrow or apprehension accompanied with the idea of the person who hates us as a cause; that is to say, we shall hate him in return, as we have said above. If we imagine that the person we love is affected with hatred towards us, we shall be agitated at the same time both with love and hatred. For in so far as we imagine that we are hated are we determined to hate him in return. But (by hypothesis) we love him notwithstanding, and therefore we shall be agitated both by love and hatred.