Another optimistic adjective, valid means actually supporting the intended point or claim. Legally or officially acceptable, to be valid is to be sound, well founded, well-grounded, substantial, reasonable, logical, justifiable, defensible, authentic, bona-fide, effective, cogent, powerful, convincing, credible, forceful, weighty.
Etymologically speaking, the root of this word is derived from the Latin ‘validus’ : strong
Additionally the French word ‘valide’ gave rise to the English word ‘valid’, meaning able-bodied.
If anyone is honest thinking about the stem of this word there are a number of optimistic words beginning with ‘val’ , for example : value, valve or valour. From my memory there is also the French word ‘valise’ meaning case or roughly translated ‘brief case’ which implies the able bodied character with this has everything they need to be morally defensible. In recent times the brief case has been somewhat superceded by the laptop and/or tablet and/or e readers.