Deceit is an artifice, since it pretends one thing and does another.

Explanation

(English-origin maxim.) The essence of deceit is the gap between appearance and reality — fraud is proven by showing that the party represented one thing while intending or doing another.

Where this applies

• A car dealer advertises a vehicle as "accident-free" while knowing it was totaled and rebuilt — the gap between his claim and reality is the very definition of deceit.
• A landlord tells prospective tenants the apartment passed inspection while secretly knowing it failed for mold — saying one thing and doing another proves the fraud.
• A contractor promises to use copper piping but installs cheap plastic — the difference between what he said and what he did is all the court needs to find deceit.