It is evident, that sympathy, or the communication of passions, takes place among animals, no less than among men. Fear, anger, courage, and other affections are frequently communicated from one animal to another, without their knowledge of that cause, which produced the original passion. Grief likewise is received by sympathy; and produces almost all the same consequences, and excites the same emotions as in our species. The howlings and lamentations of a dog produce a sensible concern in his fellows. And it is remarkable, that though almost all animals use in play the same member, and nearly the same action as in fighting; a lion, a tyger, a cat their paws; an ox his horns; a dog his teeth; a horse his heels: Yet they most carefully avoid harming their companion, even though they have nothing to fear from his resentment; which is an evident proof of the sense brutes have of each other's pain and pleasure.

Every one has observed how much more dogs are animated when they hunt in a pack, than when they pursue their game apart; and it is evident this can proceed from nothing but from sympathy. It is also well known to hunters, that this effect follows in a greater degree, and even in too great a degree, where two packs, that are strangers to each other, are joined together. We might, perhaps, be at a loss to explain this phænomenon, if we had not experience of a similar in ourselves.

Envy and malice are passions very remarkable in animals. They are perhaps more common than pity; as requiring less effort of thought and imagination.

We come now to explain the direct passions, or the impressions, which arise immediately from good or evil, from pain or pleasure. Of this kind are, desire and aversion, grief and joy, hope and fear.

Of all the immediate effects of pain and pleasure, there is none more remarkable than the WILL; and though properly speaking, it be not comprehended among the passions, yet as the full understanding of its nature and properties, is necessary to the explanation of them, we shall here make it the subject of our enquiry. I desire it may be observed, that by the will, I mean nothing but the internal impression we feel and are conscious of, when we knowingly give rise to any new motion of our body, or new perception of our mind. This impression, like the preceding ones of pride and humility, love and hatred, it is impossible to define, and needless to describe any farther; for which reason we shall cut off all those definitions and distinctions, with which philosophers are wont to perplex rather than dear up this question; and entering at first upon the subject, shall examine that long disputed question concerning liberty and necessity; which occurs so naturally in treating of the will.

It is universally acknowledged, that the operations of external bodies are necessary, and that in the communication of their motion, in their attraction, and mutual cohesion, there are nor the least traces of indifference or liberty. Every object is determined by an absolute fate to a certain degree and direction of its motion, and can no more depart from that precise line, in which it moves, than it can convert itself into an angel, or spirit, or any superior substance. The actions, therefore, of matter are to be regarded as instances of necessary actions; and whatever is in this respect on the same footing with matter, must be acknowledged to be necessary. That we may know whether this be the case with the actions of the mind, we shall begin with examining matter, and considering on what the idea of a necessity in its operations are founded, and why we conclude one body or action to be the infallible cause of another.

It has been observed already, that in no single instance the ultimate connexion of any objects is discoverable, either by our senses or reason, and that we can never penetrate so far into the essence and construction of bodies, as to perceive the principle, on which their mutual influence depends. It is their constant union alone, with which we are acquainted; and it is from the constant union the necessity arises. If objects had nor an uniform and regular conjunction with each other, we should never arrive at any idea of cause and effect; and even after all, the necessity, which enters into that idea, is nothing but a determination of the mind to pass from one object to its usual attendant, and infer the existence of one from that of the other. Here then are two particulars, which we are to consider as essential to necessity, viz, the constant union and the inference of the mind; and wherever we discover these we must acknowledge a necessity. As the actions of matter have no necessity, but what is derived from these circumstances, and it is not by any insight into the essence of bodies we discover their connexion, the absence of this insight, while the union and inference remain, will never, in any case, remove the necessity.

It is the observation of the union, which produces the inference; for which reason it might be thought sufficient, if we prove a constant union in the actions of the mind, in order to establish the inference, along with the necessity of these actions. But that I may bestow a greater force on my reasoning, I shall examine these particulars apart, and shall first prove from experience that our actions have a constant union with our motives, tempers, and circumstances, before I consider the inferences we draw from it.

To this end a very slight and general view of the common course of human affairs will be sufficient. There is no light, in which we can take them, that does nor confirm this principle. Whether we consider mankind according to the difference of sexes, ages, governments, conditions, or methods of education; the same uniformity and regular operation of natural principles are discernible. Like causes still produce like effects; in the same manner as in the mutual action of the elements and powers of nature.

There are different trees, which regularly produce fruit, whose relish is different from each other; and this regularity will be admitted as an instance of necessity and causes in external bodies. But are the products of Guienne and of Champagne more regularly different than the sentiments, actions, and passions of the two sexes, of which the one are distinguished by their force and maturity, the other by their delicacy and softness?

Are the changes of our body from infancy to old age more regular and certain than those of our mind and conduct? And would a man be more ridiculous, who would expect that an infant of four years old will raise a weight of three hundred pound, than one, who from a person of the same age would look for a philosophical reasoning, or a prudent and well-concerted action?

We must certainly allow, that the cohesion of the parts of matter arises from natural and necessary principles, whatever difficulty we may find in explaining them: And for a reason we must allow, that human society is founded on like principles; and our reason in the latter case, is better than even that in the former; because we not only observe, that men always seek society, but can also explain the principles, on which this universal propensity is founded. For is it more certain, that two flat pieces of marble will unite together, than that two young savages of different sexes will copulate? Do the children arise from this copulation more uniformly, than does the parents care for their safety and preservation? And after they have arrived at years of discretion by the care of their parents, are the inconveniencies attending their separation more certain than their foresight of these inconveniencies and their care of avoiding them by a close union and confederacy?

The skin, pores, muscles, and nerves of a day-labourer are different from those of a man of quality: So are his sentiments, actions and manners. The different stations of life influence the whole fabric, external and internal; and different stations arise necessarily, because uniformly, from the necessary and uniform principles of human nature. Men cannot live without society, and cannot be associated without government. Government makes a distinction of property, and establishes the different ranks of men. This produces industry, traffic, manufactures, law-suits, war, leagues, alliances, voyages, travels, cities, fleets, ports, and all those other actions and objects, which cause such a diversity, and at the same time maintain such an uniformity in human life.

Should a traveller, returning from a far country, tell us, that he had seen a climate in the fiftieth degree of northern latitude, where all the fruits ripen and come to perfection in the winter, and decay in the summer, after the same manner as in England they are produced and decay in the contrary seasons, he would find few so credulous as to believe him. I am apt to think a travellar would meet with as little credit, who should inform us of people exactly of the same character with those in Plato's republic on the one hand, or those in Hobbes's Leviathan on the other. There is a general course of nature in human actions, as well as in the operations of the sun and the climate. There are also characters peculiar to different nations and particular persons, as well as common to mankind. The knowledge of these characters is founded on the observation of an uniformity in the actions, that flow from them; and this uniformity forms the very essence of necessity.

I can imagine only one way of eluding this argument, which is by denying that uniformity of human actions, on which it is founded. As long as actions have a constant union and connexion with the situation and temper of the agent, however we may in words refuse to acknowledge the necessity, we really allow the thing. Now some may, perhaps, find a pretext to deny this regular union and connexion. For what is more capricious than human actions? What more inconstant than the desires of man?

And what creature departs more widely, not only from right reason, but from his own character and disposition? An hour, a moment is sufficient to make him change from one extreme to another, and overturn what cost the greatest pain and labour to establish. Necessity is regular and certain. Human conduct is irregular and uncertain. The one, therefore, proceeds not from the other.

To this I reply, that in judging of the actions of men we must proceed upon the same maxims, as when we reason concerning external objects. When any phaenomena are constantly and invariably conjoined together, they acquire such a connexion in the imagination, that it passes from one to the other, without any doubt or hesitation. But below this there are many inferior degrees of evidence and probability, nor does one single contrariety of experiment entirely destroy all our reasoning. The mind ballances the contrary experiments, and deducting the inferior from the superior, proceeds with that degree of assurance or evidence, which remains. Even when these contrary experiments are entirely equal, we remove not the notion of causes and necessity; but supposing that the usual contrariety proceeds from the operation of contrary and concealed causes, we conclude, that the chance or indifference lies only in our judgment on account of our imperfect knowledge, not in the things themselves, which are in every case equally necessary, though to appearance not equally constant or certain.