valid

1 according to the rules of logic your argument isn't valid because you're taking what should be the conclusion and using it as a premise Synonyms analytic (or analytical), coherent, consequent, good, rational, reasonable, sensible, sound, logical, well-founded, well-groundedRelated Words a posteriori, a priori, syllogistic; cognitive, empirical (also empiric); defendable, defensible, justifiable, maintainable, supportable, sustainable, tenableNear Antonyms casuistic (or casuistical), eristic (also eristical), fallacious, misleading, sophistic (or sophistical), specious; unarticulated; unscientific; absurd, cockeyed, crazy, daffy, fatuous, half-baked, half-witted, harebrained, insane, loony (also looney), mad, nonsensical, nutty, preposterous, simpleminded, stupid, weak-minded, witless; senseless, thoughtless; uncompelling, unconvincingAntonyms illegitimate, illogical, incoherent, inconsequent, inconsequential, invalid, irrational, unreasonable, unsound, weak

2 based on sound reasoning or information only further investigation will show whether your theory is valid Synonyms commonsense, commonsensible, commonsensical, firm, hard, informed, just, justified, levelheaded, logical, rational, reasonable, reasoned, sensible, sober, solid, good, well-foundedRelated Words actual, real, true; certain, sure; certified, validated, verified; confirmed, corroborated, substantiated; cogent, convincing; colorable, credible, plausibleNear Antonyms unsubstantiated, unsupported, unwarranted; flimsy, implausible, unconvincing, weak; fallacious, false, misguided, misledAntonyms groundless, illogical, invalid, irrational, nonrational, nonsensical, nonvalid, unfounded, uninformed, unjustified, unreasonable, unreasoned, unsound