In essence one cause has two manifestations. One of these manifestations is the position of the planets in the sky and the other manifestation is the position of forces represented by the planets as symbols within ourselves and hence within our lives.
The approach that the modernists take (that the planets have an objective impact in our lives) becomes problematic for a number of reasons. Are we really to believe that the Part of Cucumbers and Melons, which is not a planetary body but a calculated point based on planetary bodies, has an impact on cucumber and melon plants? Of course not. Astrology is a meta-languistic divination system, not a science in the way that, say, physics is.