Page:The Foundations of Science (1913).djvu/249

Rh range them in the causal order $$A B C D$$, and at the same time in the chronologic order $$A B C D$$, rather than in any other order?

I clearly see that in the act $$A$$ I have the feeling of having been active, while in undergoing the sensation $$D$$ I have that of having been passive. This is why I regard $$A$$ as the initial cause and $$D$$ as the ultimate effect; this is why I put $$A$$ at the beginning of the chain and $$D$$ at the end; but why put $$B$$ before $$C$$ rather than $$C$$ before $$B$$?

If this question is put, the reply ordinarily is: we know that it is $$B$$ which is the cause of $$C$$ because we always see $$B$$ happen before $$C$$. These two phenomena, when witnessed, happen in a certain order; when analogous phenomena happen without witness, there is no reason to invert this order.

Doubtless, but take care; we never know directly the physical phenomena $$B$$ and $$C$$. What we know are sensations $$B'$$ and $$C'$$ produced respectively by $$B$$ and $$C$$. Our consciousness tells us immediately that $$B'$$ precedes $$C'$$ and we suppose that $$B$$ and $$C$$ succeed one another in the same order.

This rule appears in fact very natural, and yet we are often led to depart from it. We hear the sound of the thunder only some seconds after the electric discharge of the cloud. Of two flashes of lightning, the one distant, the other near, can not the first be anterior to the second, even though the sound of the second comes to us before that of the first?

Another difficulty; have we really the right to speak of the cause of a phenomenon? If all the parts of the universe are interchained in a certain measure, any one phenomenon will not be the effect of a single cause, but the resultant of causes infinitely numerous; it is, one often says, the consequence of the state of the universe a moment before. How enunciate rules applicable to circumstances so complex? And yet it is only thus that these rules can be general and rigorous.

Not to lose ourselves in this infinite complexity, let us make a simpler hypothesis. Consider three stars, for example, the sun, Jupiter and Saturn; but, for greater simplicity, regard them as