De Libertate Mentis
There shall be no Property in Human Thought. Let each think as he will concerning the Universe; but let none seek to impose that Thought upon another by any Threat of Penalty in this World or any other World. Look now, though I enkindle thee to Effort in thy Way, yet it is the Way of thy Will, and I say not even that thou dost well to hasten therein, for the whole Matter lieth in thy Will, and to force thyself against thy Nature would be an Obstacle to thy Passage. But if I urge thee to run well this Race as an Athlete, it is because I have perceived in thy Nature that firce Lust and mighty Concentration in that Will, and I write this Letter unto thee, knowing well that thou wilt rejoice exceedingly therein, since it is an Expression of thine own Will, and it may be a Discovery thereof, which Thing thou vehemently seekest. I charge thee therefore that thou permit none to tyrannize any other in Thought, or to threaten, or in any other Wise to blaspheme the great Liberty of our Father the Sun in the Great Cosmos, or of His Vice-Regent in the Little.
 On the Freedom of the Mind