"In addition, however, to the knowledge which the student of science acquires from lectures and books, he requires intelligence which only an ample and diligent perception can give him; he needs skill which comes only by repeated experiment and long practice. His senses must be sharpened for certain kinds of observation, to detect minute differences of form, colour, solidity, smell, etc., in the object under examination; his hand must be equally trained to the work of the blacksmith, the locksmith, and the carpenter, or the draughtsman and the violin player, and, when operating with the microscope, must surpass the lace-maker in delicacy of handling the needle. Moreover, when he encounters superior destructive forces, or performs bloody operations upon man or beast, he must possess the courage and coolness of the soldier. Such qualities and capabilities, partly the result of natural aptitude, partly cultivated by long practice, are not so readily and so easily acquired as the mere massing of facts in the memory."

I highly recommend this slightly longer excerpt for an eloquent statement of what it is like to do science. The entire essay was recently reprinted in Helmholtz, Science and Culture, David Cahan, ed. Chicago: University of Chicago Press, 1995.

"You ask whether your verses are any good. You ask me. You have asked others before this. You send them to magazines. You compare them with other poems, and you are upset when certain editors reject your work. Now (since you have said you want my advice) I beg you to stop doing that sort of thing. You are looking outside, and that is what you should most avoid right now. No one can advise or help you - no one. There is only one thing you should do. Go into yourself. Find out the reason that commands you to write; see whether it has spread its roots into the very depths of your heart; confess to yourself whether you would have to die if you were forbidden to write. This most of all: ask yourself in the most silent hour of your night: must I write? Dig into yourself for a deep answer. And if this answer rings out in assent, if you meet this solemn question with a strong, simple "I must," then build your life in accordance with this necessity; your whole life, even into its humblest and most indifferent hour, must become a sign and witness to this impulse."

"We wish to question a deeply engrained habit of thinking among students of evolution. We call it the adaptationist programme, or the Panglossian paradigm. It is rooted in a notion popularized by A.R. Wallace and A. Weismann, (but not, as we shall see, by Darwin) toward the end of the nineteenth century: the near omnipotence of natural selection in forging organic design and fashioning the best among possible worlds. This programme regards natural selection as so powerful and the constraints upon it so few that direct production of adaptation through its operation becomes the primary cause of nearly all organic form, function, and behavior."

Gould, S. J. and Lewontin, R. C., "The Spandrels of San Marco and the Panglossian Paradigm: a Critique of the Adaptationist Programme," Proceedings of the Royal Society of London, Series B, Vol. 205, No. 1161 (1979), Pp. 581-598.