a commonplace book
Pluralitas non est ponenda sine necesitate. … Frustra fit per plura quod potest fieri per pauciora.
William of Ockham
Interpretations: “Pluralities should not be posited unnecessarily. For in vain is made through several things what can be done by fewer.”
Occam’s (or Ockham’s) Razor
Note that this is not an indictment of any complex reasoning, only unnecessarily complex reasoning. A good heuristic, but not a logical fallacy, technically.