Abstract -- Most research reviews are concerned with empirical findings. This one takes astrological concepts and principles, the ideas on which astrology is based, and submits them to critical evaluation. It covers recent shifts in astrological ideas, how astrologers avoid dealing with criticism, and the problems associated with (in turn) the fundamental assumptions of astrology, the origins of astrological ideas, modern psychological astrology, astrological world views, astrological symbolism, non-falsifiability, and magical influences. To be plausible astrology needs sound ideas with sound origins, and sound methods for verifying those ideas. But none of the possible origins of astrological ideas (revelation, paranormal, analogy, observation, theory) are plausible. Astrologers can explain away wrong chart interpretations by blaming the symbolism, inadvertently left out factors (such as an asteroid) method, data, the astrologer or the client. They can also dismiss the interpretation as misguided (it used to be visible events, now it is invisible inner meaning). So astrologers could never know if astrology was wrong or which of their explanatory theories could actually apply. Central ideas such as "as above so below" and "inter-connectedness" and the "whole chart" are too poorly developed to amount to anything useful. There is little agreement on many basic issues and on how to resolve differences among astrological techniques and ideas. Astrological symbolism is unsystematic and based on metaphors, analogies, verbal associations, word play, and mythology, which are developed in different ways by different astrologers with no clear way of evaluating them. The philosophies and worldviews associated with astrology are underdeveloped or poorly described. Consequently astrology does not have the resources to put its house in order. Astrology seems quite unlikely to deliver anything beyond what non-astrological factors (eg cognitive and perceptual biases) can account for. With copious quotes from leading astrologers and nearly 250 references.