St. Paul’s precept, “No man that warreth entangleth himself with the affairs of this life.”  For they have discovered that they are engaged in a war—­a veritable war—­against the rulers of darkness, against ignorance and its twin children, fear and cruelty.  Of that war they see neither the end nor even the plan.  But they are ready to go on; ready, with Socrates, “to follow reason withersoever it leads;” and content, meanwhile, like good soldiers in a campaign, if they can keep tolerably in line, and use their weapons, and see a few yards ahead of them through the smoke and the woods.  They will come out somewhere at last; they know not where nor when:  but they will come out at last, into the daylight and the open field; and be told then—­perhaps to their own astonishment—­as many a gallant soldier has been told, that by simply walking straight on, and doing the duty which lay nearest them, they have helped to win a great battle, and slay great giants, earning the thanks of their country and of mankind.

And, meanwhile, if they get their shilling a day of fighting-pay, they are content.  I had almost said, they ought to be content.  For science is, I verily believe, like virtue, its own exceeding great reward.  I can conceive few human states more enviable than that of the man to whom, panting in the foul laboratory, or watching for his life under the tropic forest, Isis shall for a moment lift her sacred veil, and show him, once and for ever, the thing he dreamed not of; some law, or even mere hint of a law, explaining one fact; but explaining with it a thousand more, connecting them all with each other and with the mighty whole, till order and meaning shoots through some old Chaos of scattered observations.

Is not that a joy, a prize, which wealth cannot give, nor poverty take away?  What it may lead to, he knows not.  Of what use it may become, he knows not.  But this he knows, that somewhere it must lead; of some use it will be.  For it is a truth; and having found a truth, he has exorcised one more of the ghosts which haunt humanity.  He has left one object less for man to fear; one object more for man to use.  Yes, the scientific man may have this comfort, that whatever he has done, he has done good; that he is following a mistress who has never yet conferred aught but benefits on the human race.

What physical science may do hereafter I know not; but as yet she has done this: 

She has enormously increased the wealth of the human race; and has therefore given employment, food, existence, to millions who, without science, would either have starved or have never been born.  She has shown that the dictum of the early political economists, that population has a tendency to increase faster than the means of subsistence, is no law of humanity, but merely a tendency of the barbaric and ignorant man, which can be counteracted by increasing manifold by scientific means his powers of producing food.