“A central thesis of this book is that the connection between thought and practice is most intimately and fully realized only when our minds are addressed to our own affairs—the concerns of humanity. When we direct our thoughts to nature, even if to see ourselves as fixtures of nature, we loosen the connection between thought and practice. When we loosen it, we are tempted to assume the posture I earlier called naturalism. We survey both the human and the nonhuman worlds from a supposedly godlike distance. We treat the achievement of such distance as the realization of our longing for transcendence.”

"On the Conservation of Force" (1862), p. 279
Popular Lectures on Scientific Subjects (1881)

Source: Everyday Peace: Letters for Life, 2000, p.34

Source: Psychology and Its Use (1933), p. 9

The Voice of the Earth: An Exploration of Ecopsychology (2001)
Context: If we could assume the view of nonhuman nature, what passes for sane behavior in our social affairs might seem madness. But as the prevailing reality principle would have it, nothing could be greater madness than to believe that beast and plant, mountain and river have a "point of view." …minds exist, so we believe, nowhere but in human heads.

Book X, 1172a.17
Nicomachean Ethics

Napoleon : In His Own Words (1916)

How to Meditate: A Practical Guide to Making Friends with Your Mind (2008)

The Social Contract: A Personal Investigation into the Animal Origins of Order and Disorder (1970)

A Vindication of Natural Society (1756)
Context: We are indebted for all our miseries to our distrust of that guide, which Providence thought sufficient for our condition, our own natural reason, which rejecting both in human and Divine things, we have given our necks to the yoke of political and theological slavery. We have renounced the prerogative of man, and it is no wonder that we should be treated like beasts. But our misery is much greater than theirs, as the crime we commit in rejecting the lawful dominion of our reason is greater than any which they can commit. If, after all, you should confess all these things, yet plead the necessity of political institutions, weak and wicked as they are, I can argue with equal, perhaps superior, force, concerning the necessity of artificial religion; and every step you advance in your argument, you add a strength to mine. So that if we are resolved to submit our reason and our liberty to civil usurpation, we have nothing to do but to conform as quietly as we can to the vulgar notions which are connected with this, and take up the theology of the vulgar as well as their politics. But if we think this necessity rather imaginary than real, we should renounce their dreams of society, together with their visions of religion, and vindicate ourselves into perfect liberty.