ἰσχυριστέον
From LSJ
γελᾷ δ' ὁ μωρός, κἄν τι μὴ γέλοιον ᾖ → the fool laughs even when there's nothing to laugh at
English (LSJ)
A one must maintain stoutly, Pl.R.533a.
Greek (Liddell-Scott)
ἰσχῡριστέον: ῥημ. ἐπίθ. τοῦ ἰσχυρίζομαι, δεῖ ἰσχυρίζεσθαι, Πλάτ. Πολ. 533Α.