When we think of the major threats to our national security, the first to come to mind are nuclear proliferation, rogue states and global terrorism. But another kind of threat lurks beyond our shores, one from nature, not humans – an avian flu pandemic.

I am proud to have been born in Iowa. Through the eyes of a ten-year-old boy, it was a place of adventure and daily discoveries – the wonder of the growing crops, the excitements of the harvest, the journeys to the woods for nuts and hunting, the joys of snowy winters, the comfort of the family fireside, of good food and tender care.

The threat and use of violence is stimulating nuclear proliferation along with jihadi terrorism.

Slave to no sect, who takes no private road, But looks through Nature up to Nature’s God.

What constitutes a real, live human being is more of a mystery than ever these days, and men each one of whom is a valuable, unique experiment on the part of nature are shot down wholesale.

I’d rather learn from one bird how to sing than teach ten thousand stars how not to dance.

O wise man! Give your wealth only to the worthy and never to others. The water of the sea received by the clouds is always sweet.

Nature never deceives us; it is we who deceive ourselves.

Even if I knew that tomorrow the world would go to pieces, I would still plant my apple tree.

I wanted to live deep and suck out all the marrow of life, to live so sturdily and Spartanlike as to put to rout all that was not life.

See that the imagination of nature is far, far greater than the imagination of man.

Sensual love deceives one as to the nature of heavenly love; it could not do so alone, but since it unconsciously has the element of heavenly love within it, it can do so.

Walking is man’s best medicine.

The clearest way into the Universe is through a forest wilderness.

Light is the greatest disinfectant in nature and also in organizations.

I care to live only to entice people to look at Nature’s loveliness. Heaven knows that John the Baptist was not more eager to get all his fellow sinners into the Jordan than I to baptize all of mine in the beauty of God’s mountains.

Horses make a landscape look beautiful.

All the world lies warm in one heart, yet the Sierra seems to get more light than other mountains. The weather is mostly sunshine embellished with magnificent storms, and nearly everything shines from base to summit – the rocks, streams, lakes, glaciers, irised falls, and the forests of silver fir and silver pine.

Our nature consists in motion; complete rest is death.

The unnatural, that too is natural.

Nature hath framed strange fellows in her time.

The sky is the part of creation in which nature has done for the sake of pleasing man.

I thank you God for this most amazing day, for the leaping greenly spirits of trees, and for the blue dream of sky and for everything which is natural, which is infinite, which is yes.

Reality must take precedence over public relations, for nature cannot be fooled.

In the world there is nothing more submissive and weak than water. Yet for attacking that which is hard and strong nothing can surpass it.

All art is but imitation of nature.

It’s wonderful to climb the liquid mountains of the sky. Behind me and before me is God and I have no fears.

No nation should stoke instability in its neighbor’s country.

A few minutes ago every tree was excited, bowing to the roaring storm, waving, swirling, tossing their branches in glorious enthusiasm like worship. But though to the outer ear these trees are now silent, their songs never cease.

If a man walks in the woods for love of them half of each day, he is in danger of being regarded as a loafer. But if he spends his days as a speculator, shearing off those woods and making the earth bald before her time, he is deemed an industrious and enterprising citizen.

It is a curious thing: man, the centre and creator of all science, is the only object which our science has not yet succeeded in including in a homogeneous representation of the universe. We know the history of his bones, but no ordered place has yet been found in nature for his reflective intelligence.

Sisters are brittle things. God was penurious with me, which makes me shrewd with Him. One is a dainty sum! One bird, one cage, one flight; one song in those far woods, as yet suspected by faith only!

We are by nature observers, and thereby learners. That is our permanent state.

Oh, these vast, calm, measureless mountain days, days in whose light everything seems equally divine, opening a thousand windows to show us God.

I’m crepuscular.

When you go to the mountains, you see them and you admire them. In a sense, they give you a challenge, and you try to express that challenge by climbing them.

Studies perfect nature and are perfected still by experience.

If we had a keen vision of all that is ordinary in human life, it would be like hearing the grass grow or the squirrel’s heart beat, and we should die of that roar which is the other side of silence.

Forget not that the earth delights to feel your bare feet and the winds long to play with your hair.

Even with all of the things that are so awful, if you walk into your yard and stay there looking at almost anything for five minutes, you will be stunned by how marvelous life is and how incredibly lucky we are to have it.

During my first years in the Sierra, I was ever calling on everybody within reach to admire them, but I found no one half warm enough until Emerson came. I had read his essays, and felt sure that of all men he would best interpret the sayings of these noble mountains and trees. Nor was my faith weakened when I met him in Yosemite.

Everything is political. I will never be a politician or even think political. Me just deal with life and nature. That is the greatest thing to me.

True Scouts are the best friends of animals, for from living in the woods and wilds, and practising observation and tracking, they get to know more than other people about the ways and habits of birds and animals, and therefore they understand them and are more in sympathy with them.

Electrical science has disclosed to us the more intimate relation existing between widely different forces and phenomena and has thus led us to a more complete comprehension of Nature and its many manifestations to our senses.

I am concerned for the security of our great Nation; not so much because of any threat from without, but because of the insidious forces working from within.

America must not ignore the threat gathering against us. Facing clear evidence of peril, we cannot wait for the final proof, the smoking gun that could come in the form of a mushroom cloud.

The world is mud-luscious and puddle-wonderful.

One of the best ways to see tree flowers is to climb one of the tallest trees and to get into close, tingling touch with them, and then look broad.

The professed function of the nuclear weapons on each side is to prevent the other side from using their nuclear weapons. If that’s all it is, then we’ve gotta as: how many nuclear weapons do you need to do that?

Necessity is the mistress and guide of nature. Necessity is the theme and inventress of nature, her curb and her eternal law.

Poets say science takes away from the beauty of the stars – mere globs of gas atoms. I, too, can see the stars on a desert night, and feel them. But do I see less or more?

When a man wants to murder a tiger he calls it sport; when a tiger wants to murder him he calls it ferocity.

My love is a hummingbird sitting that quiet moment on the bough, as the same cat crouches.

I didn’t want to set up a women’s studies program. I thought women should learn to operate in a coeducational atmosphere, because, especially in national security and international affairs, it’s male-dominated.

I am against nature. I don’t dig nature at all. I think nature is very unnatural. I think the truly natural things are dreams, which nature can’t touch with decay.

I experience a period of frightening clarity in those moments when nature is so beautiful. I am no longer sure of myself, and the paintings appear as in a dream.

To us also, through every star, through every blade of grass, is not God made visible if we will open our minds and our eyes.

It is the nature of truth in general, as of some ores in particular, to be richest when most superficial.

Even though I write about the human race, the further away from them, the better I feel. Two miles is great; two thousand miles is beautiful.

I value my garden more for being full of blackbirds than of cherries, and very frankly give them fruit for their songs.

ISIS is not an existential threat to something happening to someone in the United States of America. It’s a serious problem overseas, but it’s confusing and frightening.