We don't have synonyms for first causes yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are first cause, first bases and first classes.
(n) :
(theology, philosophy, sometimes capitalized) An initial cause from which all other causes and effects follow.
(n) :
Alternative spelling of first cause. [(theology, philosophy, sometimes capitalized) An initial cause from which all other causes and effects follow.]
(n) :
(theology, philosophy, sometimes capitalized) An initial cause from which all other causes and effects follow.
(n) :
Alternative spelling of first cause. [(theology, philosophy, sometimes capitalized) An initial cause from which all other causes and effects follow.]