We know the effects of many things, but the causes of few; experience, therefore, is a surer guide than imagination, and enquiry than conjecture. But those physical difficulties which you cannot account for, be very slow to arraign, for he that would be wiser than nature would be wiser than God.
I sometimes use the word cause to signify any antecedent with which a consequent event is so connected that it truly belongs to the reason why the proposition which affirms that event is true, whether it has any positive influence or not.
The wise and learned amongst the very heathens themselves have all acknowledged some first cause whereupon originally the being of all things dependeth; neither have they otherwise spoken of that cause than as an agent, which knowing what and why it worketh, observeth in working a most exact order or law.
Various theories of causation have been propounded. It appears, however, to be agreed that, although in every instance we actually perceive nothing more than that the event, change, or phenomenon B always follows the event, change, or phenomenon A, yet that we naturally believe in the existence of some unknown quality or circumstance belonging to the antecedent A, in virtue of which the consequent B always has been, is, and will be, produced.
To every thing we call a cause we ascribe power to produce the effect. In intelligent causes, the power may be without being exerted; so I have power to run when I sit still or walk. But in inanimate causes we conceive no power but what is exerted, and therefore measure the power of the cause by the effect which it actually produces. The power of an acid to dissolve iron is measured by what it actually dissolves.