I would reject the offer to become a cyborg because the possible disadvantage of the loss of some or all of my humanity, of what makes me human, far outweighs the possible advantages. The stated advantages are hardly guaranteed, in any case. As with any machine which "consists, to a large degree, of artificial parts," I, as a cyborg, would be susceptible to every sort of breakdown to which all machines are susceptible. No machine, certainly no machine as technologically complex as a cyborg, is guaranteed anything. Machines of every sort, from automobiles to computers, "die" and wind up on various junk heaps every day, even brand new ones which are said to have "greater longevity of life." There is no guarantee, then, that I will not be a "lemon," that I will truly have "enormous increase in knowledge and thinking speed and a much greater longevity of life."
Even if these promises were kept by my makers and maintainers, the even more essential question of the quality of my life as a cyborg remains. The essences of being human are freedom and spirit. Neither is a part of cyborg existence. I may have the capacity for a sort of mechanical reason, just as a computer is able to perform linear tasks indicating alignment with cause and effect. However, the cyborg, as a machine, is incapable of emotion, of the reason of the heart, of spiritual considerations. The cyborg is programmed to do as the maker wishes, and no machine can be programmed with a soul, the mysterious core of humanity. Socrates puts it this way in Phaedo, in what may fairly be taken as a suggestion of the difference between a human and a machine: "When death attacks a man, the mortal portion of him may be supposed to die, but the immortal retires at the approach of death and is preserved safe and sound" (Plato 144-145). The machine dies and leaves nothing but a pile of gears and bytes' the human dies and a soul remains.
Of course, the preservation of the soul after ...