This modification entails using modern technology to further develop the human condition. I would argue, however, that this is already in effect and so we are already transhuman. Consider: one of the goals of transhumanism is to increase human longevity. But we've already accomplished this! The life expectancy of humans have increased enormously in the past century:
Another reason I hoped to talk about transhumanism is to hear the arguments against it. Coming from a technological perspective, I have yet to find any logical criticisms. The two arguments I've seen are that transhumanism a) unnatural and b) wrong for trying to play God. As an agnostic (leaning towards atheism), the latter argument holds little wait for me and I cannot rebut simply because I'm not sure how to argue against religion. The former argument, however, is trivial. Society lives already with 'unnatural' things apart of daily life: cell phones, cars, electricity, nylon, radiation therapy and antibiotics, glasses and laser eye surgery, global positioning systems and their associated satellites, blood transfusions, computers, etc, not to mention numerous scientific achievements not seen in daily life, like invisible lasers powerful enough to char a chicken in seconds or to shoot down aircraft and particle accelerators able to speed particles to almost the speed of light and smash them together. If we are to equate "unnatural" to "bad", then I suppose we should also eliminate all these things form our lives as well.
I was surprised to find that the "founder of transhumanism" is Julian Huxley, a mid-1900s biologist. He coined the term in article in which he describes humanity's ability to "transcend itself." This particularly interested me since his younger brother, Aldous Huxley, is the well-known author of Brave New World. In this novel, the main character lives in a utopian society (or dystopian, depending on your perspective) in which humans are genetically engineered down to very particular details, like whether or not you enjoy nature or flowers. I wonder if Aldous' book aimed to criticize his brother's ideas (although I don't think it was, since Julian Huxley described transhumanism a quarter century after Brave New World was initially published).
Through all of my reading, transhumanism seems an interesting route to the future. While not all aspects of it appeal to me (like cryogenics), the whole process of these advancements inspire numerous possibilities for the future.