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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
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.
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
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, concerned entirely with the bare order of sensible facts: but from these it is the very object of induction to lead him to higher principles, to guide him to the contemplation of the wider generalizations which open to him as his view enlarges, as he is continually rising to more elevated laws and loftier abstractions.
We recur, then, to the accurate study of induction, in order to understand the ground of a rational conception of physical causes : which is, in fact, no other than that on which all sound induction proceeds: the extended evidence of natural analogies: the conviction of a close union and conspiring harmony throughout the whole range of natural phenomena; such that we cannot imagine even a partial dissociation which would not entail more extensive disarrangements, and involve a disorganization, of the system of material things.
It is the combined force of many conspiring relations which tends to impress the mind with a persuasion of the intimate connexion between physical phenomena which we call cause and effect. It is this support which each distinct truth ministers to another; this mutual corroboration and confirmation of physical laws, which constitutes the notion we can hardly avoid forming, of a consolidating and connecting power, or efficient causation, between phenomena, which maintains them in union. This confederacy of causes, (as Bacon* emphatically
* De Augmentis. I.
terms it,) this adjustment of one to the other, it is, which compacts the whole series of physical laws, in a self-supporting equilibrium, like the stones of an arch, so that we cannot conceive the removal of one portion without the destruction of the whole.
We shall thus be prepared to pursue the highest and most important considerations which arise out of the philosophy of physical causes. We connect those causes with universal laws; we learn those laws from inductive evidence: and the combined effect of the whole body of physical induction is to demonstrate the immutable uniformity and recondite adjustment pervading all nature. And the further inductive generalization, or, in other words, the study of physical causes, may be carried, the more abundantly do we find those conclusions confirmed. The mutual corroboration and conspiring testimony of endless concurrent inductions, advances and augments, in an accumulating ratio the overwhelming evidence of order and arrangement, of analogy and harmony, throughout the physical world.