I proceed now to examine some particular kinds of liberty which have been claimed as natural rights. In the life of man we very commonly distinguish three main forms in which his natural powers can be exercised – thought, speech, action. Action is a very wide term, and clearly requires subdivision; but we may take these three main forms as distinguishing three spheres in which freedom may be claimed. Freedom of thought in one sense, which may fairly be regarded as the strictest sense of the words, everyone has, and nobody can restrict. The Holy Office many forbid a man to utter any doctrine of which it does not approve, but no power that priest or tyrant has ever wielded can limit the freedom of a man’s inmost soul. And, under oppression and amid bigotry, the closed lips of the intellectual rebel have often smiled bitterly but proudly, conscious of a freedom which even stone walls and iron bars cannot limit or confine. But to think what may not be uttered becomes a torture which eats away the soul. And the intellect which is shut up in its own dark chamber tends to pine away and perish, missing alike the fresh air of controversy and the sunshine of human sympathy. Indirectly, if not directly, even this sad privilege of freedom of thought is destroyed by systematic repression of freedom of utterance. And in any sense of the words which goes beyond the merely negative one – that what goes on in ones mind cannot be directly controlled by others – freedom of thought cannot exist except in a stimulating intellectual atmosphere. For freedom of thought, in the positive sense of the development of intellectual capacity and the earnest pursuit of truth, implies the existence of a good system of education, of a high average of intellectual culture in at least some class of the community, and of the possibility of a satisfactory career for those who devote themselves especially to intellectual pursuits.
The mere absence of laws interfering with intellectual liberty will not of itself lead to the growth of a genuinely scientific spirit in regard to matters of belief. The public opinion of a society of uneducated or slightly educated persons, who are more or less under the sway of the same beliefs in religious, political, or social matters, may be far more adverse to the growth of any true positive intellectual liberty than even the existence of considerable legal restrictions on the free expression of opinion in popular discourses, provided that a certain degree of license is permitted, or winked at, in the case of those who address a limited audience of the learned. In a democratically governed society there may, owing to the strong pressure of popular prejudice, be less intellectual liberty, negative or positive, than under certain kinds of aristocratic and even of despotic governments. In the latter cases freedom of thought may be the privilege only of the few, and it may be a privilege dependent on the somewhat uncertain caprice of those in power; but in the former case it may be practically non-existent. A strong government, even of despotic or arbitrary kind, is often necessary in order to secure the person who holds some unpopular opinion against the hatred of the bigoted multitude. Under the early Roman Empire, Greek sceptics and Christian believers enjoyed an amount of security and liberty which no champions of new and unpopular opinions could possibly have enjoyed in a small democracy or in Puritan Massachusetts, so long as such communities remained homogeneous in their religious beliefs.