I have come to think of pseudoscience as sciences shadow. A shadow is cast by something; it has no substance of its own. The same is true for these doctrines on the fringe. If scientists use some criterion such as peer review to demarcate, so will the fringe (creationists have peer-reviewed journals, as did Velikovskians). The brighter the light of sciencethat is, the greater its cultural prestige and authoritythe sharper the shadow, and the more the fringe flourishes.
