Benjamin Franklin

Dear Friend,

Your kind letter of September 27 came to hand October 21, and the books you sent me have been received with many thanks.

The rapid progress true science now makes occasions my regretting sometimes that I was born so soon. It is impossible to imagine the height to which may be carried, in a thousand years, the power of man over matter. We may perhaps learn to deprive large masses of their gravity, and give them absolute levity, for the sake of easy transport.

Agriculture may diminish its labor and double its produce; all diseases may by sure means be prevented or cured, not excepting even that of old age, and our lives lengthened at pleasure even beyond the antediluvian standard. O that moral science were in as fair a way of improvement, that men would cease to be wolves to one another, and that human beings would at length learn what they now improperly call humanity!

I am glad my little paper on the Aurora Borealis pleased. If it should occasion further inquiry, and so produce a better hypothesis, it will not be wholly useless. I am ever, with the greatest esteem and affection, dear sir, your most obedient humble servant.

But you question, What signifies Philosophy that does not apply to some Use? But if you had never studied the Nature of Air, and the Properties of its different Kinds, if you had not discovered the Method of producing that dephlogisticated Air from a Variety of Substances, we should never have enjoyed the immense Advantage of breathing dephlogisticated Air, as a Remedy for putrid Diseases.

Your Discoveries relating to Air, though they appeared merely speculative, have from their first Publication been actually applied to the most important Uses; and here I will mention some Particulars that have come within my Knowledge.

Dr. Ingenhousz, some years since, informed me that he had with great Success treated several Persons in putrid Fevers, by confining them in Chambers filled with dephlogisticated Air. The Patients recovered much sooner than they could probably have done in common Air; and he thought Lives were saved by the Practice.

Your Method of procuring this pure Air from Plants, by exposing them to the Sun’s Light under Water, has enabled us to obtain it in large Quantities; and Experiments have since been made that show its admirable Effects in sweetening putrid Water, and rendering the foulest Air respirable and healthy.

These are no small Matters. When we consider the Multitudes that die yearly of putrid and malignant Fevers, and that these Lives might probably be saved by the Use of dephlogisticated Air, we cannot but acknowledge that your Philosophical Inquiries, though they seemed to have no immediate Relation to human Welfare, have proved of the utmost Importance to it.

Thus we see how much the Welfare of Mankind may be promoted by Attention to Branches of Knowledge, which appear to be merely curious, and of no immediate Benefit. The Compass was not invented by one who foresaw its Use in Navigation; nor was the Mariner’s Needle first magnetized by one who intended it for the Direction of Seamen.

All the Knowledge Man has of Nature, all his Control over its Forces, all his Understanding of the Laws of Existence, have been developed, and can only be developed, by the free Action of the Mind upon the Materials which the Universe supplies. Each Increment of Knowledge may lead to some immediate Practical Good; but it is more likely to lead to some other Addition to Knowledge, and this to another, and so on, each Link in the Chain being forged in Freedom, for its own sake.

B. Franklin