"He that can swim needs not despair to fly; to swim is to fly in a grosser fluid, and to fly is to swim in a subtler. We are only to proportion our power of resistance to the different density of matter through which we are to pass. You will be necessarily upborne by the air if you can renew any impulse upon it faster than the air can recede from the pressure."

Previous Quote

It is not the bigness of anything in this kind that can hinder its motion, if the motive faculty be answerable thereunto. We see a great ship swims as well as a small cork, and an eagle flies in the air as well as a little gnat. 'Tis likely enough that there may be means invented of journeying to the Moon; and how happy they shall be that are first successful in this attempt.

— John Wilkins