“For the moment we will put aside the consideration of the effect upon others — which is so infinitely more important — and think only of the results for the man himself. It is necessary to do this because one of the objections frequently brought against vegetarianism is that it is a beautiful theory, but one the working of which is impracticable, since it is supposed that a man cannot live without devouring dead flesh. That objection is irrational, and is founded upon ignorance or perversion of facts. I am myself an example of its falsity; for I have lived without the pollution of flesh food — without meat, fish or fowl — for the last thirty-eight years, and I not only still survive, but have been during all that time in remarkably good health. Nor am I in any way peculiar in this, for I know some thousands of others who have done the same thing. I know some younger ones who have been so happy as to be unpolluted by the eating of flesh during the whole of their lives; and they are distinctly freer from disease than those who partake of such things.”

On Virginity, Chapter 11

World Wildlife Fund: British National Appeal Banquet, London (1962)
The Environmental Revolution: Speeches on Conservation, 1962–77 (1978)
Context: For conservation to be successful it is necessary to take into consideration that it is a characteristic of man that he can only be relied upon to do anything consistently which is in his own interest. He may have occasional fits of conscience and moral rectitude but otherwise his actions are governed by self-interest. It follows then that whatever the moral reasons for conservation it will only be achieved by the inducement of profit or pleasure.

Attributed to McNaughton online, this actually is a quote from an English edition of The History of the Caliph Vathek (1786) by William Thomas Beckford, as translated by Samuel Henley.
Misattributed

Appendix 1.
Laws of Form, (1969)

Source: Vegetarianism and Occultism (1913), p. 27

A Few Thoughts for a Young Man (1850)
Context: Whether a young man shall reap pleasure or pain from winning the objects of his choice, depends, not only upon his wisdom or folly in selecting those objects, but upon the right or wrong methods by which he pursues them. Hence, a knowledge what to select and how to pursue, is as necessary to the highest happiness as virtue herself. Virtue is an angel, but she is a blind one, and must ask of Knowledge to show her the pathway that leads to her goal. <!-- p. 9

Frederick Soddy's speech at the Nobel Banquet in Stockholm (10 December 1922) http://nobelprize.org/nobel_prizes/chemistry/laureates/1921/soddy-speech.html

The True Levellers Standard Advanced (1649)

Formal Logic (1847)