An older or more elaborate form of 'freemasonic,' relating to the principles, practices, or customs of Freemasons.
From 'freemason' + '-ical' (Greek -ikalis, an elaborated adjectival suffix). An 18th-19th century variant that eventually gave way to the simpler 'freemasonic.'
This is one of those words that scientists would use to sound more impressive—'freemasonical principles' sounded more scholarly than just 'masonic' in fancy old texts and philosophical writings.
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