I am in love with this world . . . I have climbed its mountains, roamed its forests, sailed its waters, crossed its deserts, felt the sting of its frosts, the oppression of its heats, the drench of its rains, the fury of its winds, and always have beauty and joy waited upon my goings and comings.

To see Earth fully we already need to love it

....success in walking is not to let your right foot know what your left foot doeth. Your heart must furnish such music that in keeping time to it your feet will carry you around the globe without knowing it.

[Nuclear weapons] now I think I mentioned around 27,000 and during the Cold War the total global arsenal was on the order of 70,000.

Travel and society polish one, but a rolling stone gathers no moss, and a little moss is a good thing on a man.

To find the universal elements enough; to find the air and the water exhilarating; to be refreshed by a morning walk or an evening saunter... to be thrilled by the stars at night; to be elated over a bird's nest or a wildflower in spring - these are some of the rewards of the simple life.

Science sees the process of evolution from the outside, as one might a train of cars going by, and resolves it into the physical and mechanical elements, without getting any nearer the reason of its going by, or the point of its departure or destination.