Karl Robert Eduard von Hartmann (23 February 1842 – 5 June 1906) was a German philosopher, independent scholar and writer.

Von Hartmann's notable ideas include the theory of the Unconscious and a pessimistic interpretation of the "best of all possible worlds" concept in metaphysics.

[3] After the great success of his first work Philosophy of the Unconscious (1869)—the publication of which led to Von Hartmann being embroiled in the pessimism controversy in Germany[4][5]—he rejected professorships offered to him by the universities of Leipzig, Göttingen and Berlin.

This success was largely due to the originality of its title, the diversity of its contents (Von Hartmann professing to obtain his speculative results by the methods of inductive science, and making plentiful use of concrete illustrations), its fashionable pessimism and the vigour and lucidity of its style.

The conception of the Unconscious, by which Von Hartmann describes his ultimate metaphysical principle is, fundamentally, not as paradoxical as it sounds, being merely a new and mysterious designation for the Absolute of German metaphysicians.

As consciousness develops, there is a constantly growing recognition of the fact that deliverance must lie in a return to the original state of non-willing, which means the non-existence of all individuals and the potentiality of the Unconscious.

[7] An examination of the rest of experience, especially such phenomena as instinct, voluntary motion, sexual love, artistic production and the like, makes it evident that Will and Idea, unconscious but teleological, are everywhere operative, and that the underlying force is one and not many.

[6] The essential feature of the morality built upon the basis of Von Hartmann's philosophy is the realization that all is one and that, while every attempt to gain happiness is illusory, yet before deliverance is possible, all forms of the illusion must appear and be tried to the utmost.

It is only through the constant attempt to gain happiness that people can learn the desirability of nothingness; and when this knowledge has become universal, or at least general, deliverance will come and the world will cease.

No better proof of the rational nature of the universe is needed than that afforded by the different ways in which men have hoped to find happiness and so have been led unconsciously to work for the final goal.

All alike are empty promises, and known as such in the final stage, which sees all human desires as equally vain and the only good in the peace of Nirvana.

[7] The relation between philosophy and religion lies in their common recognition of an underlying unity, which transcends all the apparent differences and divisions due to individual phenomena.

The criticism has been described as an attack abounding in clean hits but marred by bitter sarcasm,[15] such as "is the coitus a sacrifice the individual makes?

You must be – I repeat it – a very strangely organized being",[Note 1] and for denying Schopenhauer's deduction that the will is the thing-in-itself: "you also have the sad honor, to stand at the same level as those who have misunderstood Copernicus and still confidently believe that the sun turns around the earth.

"[Note 2] Friedrich Nietzsche offers a scathing criticism of Von Hartmann, calling his philosophy "unconscious irony" and "roguery", in the second of his Untimely Meditations, On the Use and Abuse of History for Life.