[Advice to would-be trippers, simply:] Go to the meadows, go to the garden, go to the woods. Open your eyes!

A body of work such as Pasteur’s is inconceivable in our time: no man would be given a chance to create a whole science. Nowadays a path is scarcely opened up when the crowd begins to pour in.

A work of genius is something like the pie in the nursery song, in which the four and twenty blackbirds are baked. When the pie is opened, the birds begin to sing. Hereupon three fourths of the company run away in a fright; and then after a time, feeling ashamed, they would fain excuse themselves by declaring, the pie stank so, they could not sit near it. Those who stay behind, the men of taste and epicures, say one to another, We came here to eat. What business have birds, after they have been baked, to be alive and singing? This will never do. We must put a stop to so dangerous an innovation: for who will send a pie to an oven, if the birds come to life there? We must stand up to defend the rights of all the ovens in England. Let us have dead birds..dead birds for our money. So each sticks his fork into a bird, and hacks and mangles it a while, and then holds it up and cries, Who will dare assert that there is any music in this bird’s song?

As you sit on the hillside, or lie prone under the trees of the forest, or sprawl wet-legged on the shingly beach of a mountain stream, the great door, that does not look like a door, opens.

Astronomers have built telescopes which can show myriads of stars unseen before; but when a man looks through a tear in his own eye, that is a lens which opens reaches into the unknown, and reveals orbs which no telescope, however skilfully constructed, could do.

Civilization no longer needs to open up wilderness; it needs wilderness to help open up the still largely unexplored human mind.

I can certainly wish for new, large, and properly constructed instruments, and enough of them, but to state where and by what means they are to be procured, this I cannot do. Tycho Brahe has given Mastlin an instrument of metal as a present, which would be very useful if Mastlin could afford the cost of transporting it from the Baltic, and if he could hope that it would travel such a long way undamaged… . One can really ask for nothing better for the observation of the sun than an opening in a tower and a protected place underneath.

I had at one time a very bad fever of which I almost died. In my fever I had a long consistent delirium. I dreamt that I was in Hell, and that Hell is a place full of all those happenings that are improbable but not impossible. The effects of this are curious. Some of the damned, when they first arrive below, imagine that they will beguile the tedium of eternity by games of cards. But they find this impossible, because, whenever a pack is shuffled, it comes out in perfect order, beginning with the Ace of Spades and ending with the King of Hearts. There is a special department of Hell for students of probability. In this department there are many typewriters and many monkeys. Every time that a monkey walks on a typewriter, it types by chance one of Shakespeare's sonnets. There is another place of torment for physicists. In this there are kettles and fires, but when the kettles are put on the fires, the water in them freezes. There are also stuffy rooms. But experience has taught the physicists never to open a window because, when they do, all the air rushes out and leaves the room a vacuum.

Science, Nature,—O, I’ve yearned to open some page.

Students who have attended my [medical] lectures may remember that I try not only to teach them what we know, but also to realise how little this is: in every direction we seem to travel but a very short way before we are brought to a stop; our eyes are opened to see that our path is beset with doubts, and that even our best-made knowledge comes but too soon to an end.

The dream is a little hidden door in the innermost and most secret recesses of the psyche, opening into the cosmic night which was psyche long before there was any ego-consciousness, and which will remain psyche no matter how far our ego-consciousness may extend.

The nervous system is the most complex and delicate instrument on our planet, by means of which relations, connections are established between the numerous parts of the organism, as well as between the organism, as a highly complex system, and the innumerable, external influences. If the closing and opening of electric current is now regarded as an ordinary technical device, why should there be any objection to the idea that the same principle acts in this wonderful instrument? On this basis the constant connection between the external agent and the response of the organism, which it evokes, can be rightly called an unconditioned reflex, and the temporary connection—a conditioned reflex.

The uncertainty where to look for the next opening of discovery brings the pain of conflict and the debility of indecision.

There is no one central problem in philosophy, but countless little problems. Philosophy is like trying to open a safe with a combination lock: each little adjustment of the dials seems to achieve nothing, only when everything is in place does the door open.

Years ago I used to worry about the degree to which I specialized. Vision is limited enough, yet I was not really working on vision, for I hardly made contact with visual sensations, except as signals, nor with the nervous pathways, nor the structure of the eye, except the retina. Actually my studies involved only the rods and cones of the retina, and in them only the visual pigments. A sadly limited peripheral business, fit for escapists. But it is as though this were a very narrow window through which at a distance, one can only see a crack of light. As one comes closer the view grows wider and wider, until finally looking through the same narrow window one is looking at the universe. It is like the pupil of the eye, an opening only two to three millimetres across in daylight, but yielding a wide angle of view, and manoeuvrable enough to be turned in all directions. I think this is always the way it goes in science, because science is all one. It hardly matters where one enters, provided one can come closer, and then one does not see less and less, but more and more, because one is not dealing with an opaque object, but with a window.