Astrology and the Jesuits: what was actually permitted
The usual account has the Church suppressing astrology and the subject surviving underground until the nineteenth century. The seventeenth-century record, in Portugal as elsewhere, does not support it.
Astrology was taught in Jesuit colleges. Jesuits corresponded about charts. A Jesuit could tutor a royal heir who collected nativities and made political predictions, and continue an entirely orthodox career. What was in force was not a prohibition but a distinction — and the distinction is worth understanding, because it shaped the technique itself.
Natural and judicial
Natural astrology covered the influence of the heavens on the physical world: weather, agriculture, tides, the humours, the timing of medical treatment. This was uncontroversial. It was physics, in the vocabulary of the period, and it was taught as such.
Judicial astrology covered judgements about human affairs — nativities, elections, horary questions, the fates of kingdoms. Here the objection was specific and theological: an astrologer who claims to know what a person will freely choose is claiming knowledge that belongs to God alone, and is implicitly denying free will.
The line was drawn through the middle of practice, and practitioners knew exactly where it ran. Sixtus V's bull of 1586 condemns judicial astrology while explicitly excepting judgements about agriculture, navigation and medicine. That is a distinction, not a ban.
How practitioners worked with it
Three positions were available, and all three appear in the sources.
The first was doctrinal: the stars incline but do not compel. This is Aquinas, and it is the formula that made an astrological practice compatible with orthodoxy. A chart shows dispositions; the will is free to act against them.
The second was a matter of subject. Mundane astrology concerns collectives — a kingdom, an army, a harvest — and the objection from individual free will has less purchase on the fortunes of a nation.
The third was discretion. Judgements circulated in manuscript, among people who understood them, rather than in print.
What this did to the technique
This is the part that matters for practice, rather than for history.
The doctrine of inclination is not a concession extracted from astrologers by the Church. It is a description of what the technique actually does, and it produces better astrology than the alternative. A chart states the conditions under which a thing can happen — the capacity, the promise, the timing of activation. It does not state that the native will act. Someone with every testimony for success who declines to get out of bed will not succeed, and no traditional author would find that surprising.
The modern accusation that traditional astrology is fatalistic misses this entirely. The seventeenth-century practitioner had both a theological reason and a technical reason for holding that it is not, and the two reasons are the same reason.
Our research includes the practice of astrology in Portugal between the fifteenth and eighteenth centuries, from chronicles, correspondence and archives.