The Proteans have helped many other races, including humans, to unlock the psionic potential of their mind. It requires difficult training to bring this power to light in a human, often taking years of training. While it is most common (and respected) to be taught by a Protean Archon, it is possible for humans to teach each other as well.
Psionics harness the power of a beings mind to affect the world around them, or the minds of the others. In the past, men might have called it magic – or dismissed it as illusion, if they were not of the superstitious type. Since the arrival of the contractors however, humans are much more likely to accept the possibility of the supernatural.
In Japan, psyches are legally required to be registered with the government and take courses in “Responsible Usage” of their techniques. Unfortunately, the government lacks and way to detect someone with psionic talent short of witnessing it first hand, so many psyches go unregistered.