of the connexion of physical phenomena; we trace not only one series of causes and effects, but many, and these not independent, but united by common principles. We perceive a union between extended orders of facts. We find not merely one relation established, but a communication opened, as it were, with a vast range of such relations; and many such channels of communication, widely ramifying in all directions. The great truths of the natural world are proclaimed, as it were, not merely by the accordant evidence of a few witnesses, but of a vast number; and with the increasing assurance, too, that as many more as we may summon, will all confirm each other's statement. And this not merely in one or a few points, but in connected trains of narrative; and again, not only in one or a few, but a great number of distinct narratives, all of which throw light upon, and corroborate each other; and the number and extent of which is increasing and accumulating without limit.

Ideas of Efficient Causation.

By such considerations as those now adduced, it appears to me that we obtain a view of the relation of physical cause and effect at once simple and satisfactory; divested of mystery, yet rising above the relation of a mere invariable "sequence" of facts. We find the connexion of causes and effects in the connexion of laws and principles. And in

the most strictly philosophical view of the matter, we rationally extend our notion of physical causation beyond the bare circumstance of two consecutive phenomena, to the conviction of an intimate union between them: which is no other than that of the particular individual case with the more general law of that law with some still more comprehensive principle and of this, again, in its turn, with some yet more universal theory: thus establishing not merely sequences but reasons, not merely connexions but explanations.

We may thus safely admit that our persuasion of an intimate causality (if rationally explained) is really something more than the mere influence of an ill-regulated imagination improperly intruding itself upon philosophical speculation. We thus sufficiently account for the most powerful conviction of a hidden connexion between natural events, which we experience even before the grounds of it have been distinctly analysed. In the successively higher generalizations which really constitute what is so improperly represented by the common metaphor of the "chain" of causes, we find a real and rational gratification of our longing anxiety to penetrate beyond the bare surface of sensible phenomena into the more hidden relations and mysterious combinations of nature.

If further confirmation of this view of the matter be wanting, we may find it in observing the dependence which the strength of our impression of an

intimate causality always has upon the extent to which we trace the series of combinations of laws and principles.

The force of the persuasion we entertain of causation varies with the different degrees in which the relations of physical laws are more or less general, more or less widely ramified and dependent one on another, more or less connected with high general principles and comprehensive theories. Our impression of the idea of an efficient cause is much weaker, for instance, in the case of friction and heat, than in that of gravitation and elliptic orbits, or tides.

Suppose we should hear it reported that some substance had been found in which no violence of friction would produce heat; in estimating its probability prior to evidence of the fact, I believe no truly philosophic inquirer would reject it as a violation of the order of natural causes. But suppose it should be rumoured that a new planet was discovered, but that it did not move in an elliptic orbit; I imagine this circumstance would cast suspicion on the credit of the whole statement, in the minds of all who understood the nature of gravitation.

Or, again; suppose it should be stated that at a certain port, on a certain day, the tide did not occur; rather than believe that there was actually no attraction of the water by the moon in that particular instance, we should adopt any supposition of currents, winds, &c., or even rest in the mere possibility of some counteracting cause, though wholly unable

to assign its nature, as the more probable and rational idea.

We have a far less powerful persuasion of an inseparable connexion between the action of an acid and the red colour which it produces, than of that between a high charge of atmospheric electricity, and the production of thunder. And the reason seems to be, that, in the former case, we know only the bare law that such an effect is produced: in the latter we know something (at least) of the reason why and the manner how it is produced. In the former we do not know any intermediate step in the process, any intermediate circumstance in the order of causes, we have no succession of generalizations: in the latter we can trace several. For instance: high electric tension always tends to a discharge: a sudden discharge of electricity always produces a flash and a violent concussion of the air: the concussion of the air always occasions a report in our ears. We could not imagine an instance where this ultimate effect was not produced without a violation of several distinct laws of nature. In the former case only one law would be violated if the effect did not take place. Now so firm is our persuasion of the uniformity of nature, that we cannot bring ourselves to believe in the capricious violation even of one of her laws; we, therefore, are prone to regard the violation of several in succession, as absolutely contradictory and impossible.

Conclusion.

THE study of physical causes has been by some writers disparaged and calumniated as of a low and confined character; as being wholly limited to the bare investigation of facts, and as incapable of rising above such knowledge as is directly conveyed by the

senses.

The view in which we have here contemplated it, will completely vindicate it from this charge. It is manifest, from what has been advanced, that the study of physical causes, even in the strictest sense, involves the very highest abstractions, the exercise of intellectual combinations, of a nature the most widely remote from the evidence of sense.

We have traced a gradation of meaning, from the bare law that one phenomenon is invariably joined and co-extensive with another, up to associations of facts and laws of successively higher generality; we assign causes of a better and more satisfactory nature, by assigning more general theories or systems of truths to which the particular cases or effects are to be referred.

In this point of view, then, the study of physical causes becomes identified with that of the general laws of the natural world. And it is here, therefore, that the nature of causation is found to be immediately connected with that of induction, by which alone those laws are elicited and established.

The experimenter is, doubtless, in the first instance,