set against it: the complexity of the subject makes its claim of providing reliable foreknowledge unattainable; reliable foreknowledge—if it can be attained—would imply such fatalism as to make the subject's purpose useless (since if the future is predictable, anything which is destined to happen will happen whether predicted or not). Ptolemy then answers each criticism in the following two chapters. Argument on the extent of astrology's reliability In chapter two Ptolemy maintains that knowledge gained by astronomical means is attainable and he attempts to define its limits according to "Aristotelian-Stoic" logic. He points out how the Sun has the greatest influence upon the Earth's seasonal and daily cycles, and that most things in nature are synchronised by the Moon: He extends this ability to stir the weather and steer the biological patterns of earthly creatures to the fixed stars and planets, so that everything which experiences cycles of growth, or patterns of behaviour, is in some way responsive to the celestial cycles. These bring about elemental changes (hot, windy, snowy or watery conditions, etc): led by the Sun, activated by the Moon and aided by the planetary configurations and the fixed stars' phenomena. The prevailing meteorological qualities are then considered to determine the temperament – the quality of the moment of time at a specific place – which is presumed to be impressed, as a sort of temporal imprint, upon the seed of anything which comes into germination or manifestation at that moment in time. Ptolemy admits that successful analysis of this temperament is not easily attained but is capable of being determined by someone who is able to regard the data "both scientifically and by successful conjecture". He questions why, if a person can reliably predict the general weather patterns and their effects upon agricultural seeds and animals from the knowledge of the celestial cycles: Whilst suggesting that such arguments are enough to demonstrate the validity of astrology, Ptolemy accepts that many mistakes are made in its practice – partly because of "evident rascals" who profess to practice it without due knowledge and pretend to foretell things which cannot be naturally known (sometimes using the term 'astrology' for practices which are not true to the genuine study of astrology) and because legitimate practitioners must acquire a magnitude of knowledge and experience within a limited life-span. His summary is that the study is usually only able to give reliable knowledge