When discussing the relationship between transhumanism and humanism, some would claim that transhumanism rejects humanism due to the latter’s limiting aspects, while others hold that transhumanism is the logical extrapolation of humanism. I firmly adhere to the latter view.
The Wikipedia definition of humanism is rather broad: “Humanism is a group of philosophies and ethical perspectives which emphasize the value and agency of human beings, individually and collectively, and generally prefers individual thought and evidence (rationalism, empiricism) over established doctrine or faith (fideism).” Historically, the advocacy of human agency and value has often led to humanists resisting static definitions of “human nature” (for instance, as advocated by various premodern religions) in favor of a melioristic view of progress and human potential. My own essay, “Human Nature is Tautological” (also available in video form) is an example of this position.
Indeed, I have often thought that humanism and transhumanism are separated only by the degree of emphasis on human improvability. Transhumanism takes the melioristic aspirations of humanism to a new level by emphasizing the power of technology to radically transform human lives by lifting age-old limitations. But nothing in humanism per se would resist such a radical transformation. Transhumanism, in my view, accepts the core values of humanism and takes them further in light of the recognition of technological possibilities, particularly as regards radical life extension and extension of human reach to both the mega-scale (space colonization and giant construction projects) and to the nano-scale (nanotechnology and its applications to manufacturing and medicine).