Inhuman Thoughts is a philosophical exploration of the possibility of increasing the physiological and psychological capacities of humans to the point that they are no longer biologically, psychologically, or socially human. The movement is from the human through the trans-human, to the post-human. The tone is optimistic; Seidel argues that such an evolution would be of positive value on the whole. Seidel's initial argument supports the need for a comprehensive ethical theory, the success of which would parallel that of a large-scale scientific revolution, such as Newtonian mechanics. He...

Immortal Passage: Philosophical Speculations on Posthuman Evolution defends the posthuman hypothesis: that descendants of present humans, leading lives of indefinitely extended duration, and having significantly altered biological, psychological, and social characteristics, will have lives superior to those of current humans. A detailed speculative account of these lives, with attention to philosophical issues raised by such an account, presents the major philosophical challenge of Immortal Passage.