Esotericists have, among many other things, conjured spirits, received messages from disincarnate beings, cast spells, interpreted horoscopes, and healed people by manipulating invisible “energies” that purportedly flow through the body. For at least some outside observers, this plethora of beliefs and practices is so outlandish that they have been led to wonder, in the words of sceptic Michael Shermer, why people believe “weird things.” The study of religions has developed a range of answers – cognitive, sociological, and historical – to the question of why people believe in the things they do. The issue of whether any of those beliefs are, to borrow Shermer's term, weird or irrational is another matter entirely.
Many people seem to find the purported irrationality of others to be a pressing issue: a vast literature exists in which entire fields of human activity are denounced as profoundly deluded. One fundamental problem with a sizeable part of that literature and its reactions to questions such as “is magic/channelling/astrology/healing irrational” is that the answers are often based upon little more than a subjective comparison between one's own cherished beliefs and those of others. It can, for instance, be deemed quite unremarkable to believe in the Trinity or the resurrection of Christ, while it is seen as irrational, weird, or even stupid to assume that the movements of the planets have anything to do with our character and destiny, or that reincarnation in a new body awaits us after death. For various reasons, not least in order to avoid the taint of being associated with this particular form of subjective mud-slinging, historians of religion have claimed that they either cannot or should not pass judgment on the behaviours and ideas of the people they study. This reluctance has deep historical roots: the founding father of the academic study of religion, Max Müller, defined the fledgling field as the value-free investigation of religious phenomena.
Besides using the words “rational” and “irrational” as subjectively wielded epithets, there are many cases where it seems appropriate to use the terms in some gut-level, pre-theoretical sense. If your long-term goal in life is to preserve your physical well-being, you will be more likely to achieve your goal by eating healthy food, refraining from smoking, and getting enough exercise than by casting spells against disease-bearing demons.