The term is a compound of the Greek words astron (star) and logos (wisdom). Astrology is thus described as a system that perceives a deeper meaning in the movement of the celestial bodies which is related to humans and events on this planet. A connection is made between planetary movements and events in a particular location and their subsequent unfolding at particular times. The horoscope serves as the basis for these calculations, and because a horoscope is always calculated for a specific location, astrology works with the geocentric model.
Astrology began with the observation of certain planetary movements, meaning that it couldn't really be viewed separately from astronomy. However, the interpretation of these movements meant that it went beyond the domain of astronomy. In modern times, astronomy has sought to distance itself from astrology.
In astrology, an almost forgotten understanding of time plays a central role. According to this way of thinking, time has both quantitative and qualitative aspects. If we observe the quality of time at the beginning of a process – and astrology does just that and erects a horoscope for that time – we can discern the innate qualities of that process which seek realisation.
Astrology can be divided into two basic branches – personal astrology and mundane astrology. Personal astrology - as the name implies - is concerned with the lives of individuals, whereas mundane astrology is concerned with certain areas, places and countries.
In both of these branches, the techniques of prognostic astrology and comparative astrology can be applied to the natal chart. In individual astrology, the natal chart is the birth chart of a person, whereas in mundane astrology, it could be for example a national horoscope or the "birth" of a significant national or international event.
Prognostic astrology compares current or future events in relation to the natal chart and tries to foresee possible developments (prognosis, prognostic method). Until recently, this was a main aspect of astrology, and it continues to be widely practiced in Asia.
Comparative astrology compares the relationship between at least two horoscopes, and attempts to draw conclusions regarding the quality of the relationship. As with prognostic astrology, this method is not exclusively restricted to actual individuals – any two horoscopes can be compared with each other.
Today, the most important theoretical foundation is the so-called Revised Astrology which is based on the model of Classical Astrology but rejects many of its evaluations, in particular its determinism.
However, because astrology does not fit into any standard scientific category and cannot be objectively proven, much depends on the astrologer's individual interpretation. There are two different models – causality and analogy. The causal model is based on the idea that celestial bodies directly influence events here on Earth. The supporters of this model point to the example of the Moon whose gravitational influence effects, among other things, the tides, plant growth and women's menstrual cycle – phenomena whose existence is not denied by science. According to this theory the other planets exert similar influences which, because of their far more subtle nature, are difficult to measure. The proponents of the analogical model consider the planets to be indicators of events on Earth without any causal connection. In this case, the planets are seen as a kind of measuring instrument, similar to a thermometer or a clock, which indicate rather than influence temperature and time. The supporters of this model refer to the famous quote from Hermes Trismegistos "as above so below" according to which the micro-cosmos – what happens on this planet - is a reflection of the macro-cosmos (the heavens). The patterns above find concrete expression here on Earth. In over thousands of years of observing natural phenomena and the heavens, humans have learnt to recognise the analogies in planetary patterns which led to the development of systematic astrological knowledge. The analogous model has numerous supporters among contemporary astrologers. C.G. Jung called this principle synchronicity, which is the premise that events occurring simultaneously are meaningfully connected, even though there is no causal relationship between them.
- Woodcut by Flammarion (1888).