" validly "

1: as in fairly, justifiably;

•  Synonyms : 

•  excusably,

•  fairly,

•  justifiably,

•  pleasantly,

•  discreetly,

•  judiciously,

•  prudently,

•  sensibly,

•  wisely,

•  considerately,

•  courteously,

•  graciously,

•  kindly,

•  nicely,

•  reasonably,

•  thoughtfully,

•  well,

•  chivalrously,

•  decorously,

•  deferentially,

•  gallantly,

•  politely,

•  respectfully,

•  solicitously,

•  compassionately,

•  humanely,

•  kindheartedly,

•  sweetly,

•  sympathetically

•  Antonyms : 

•  discourteously,

•  inconsiderately,

•  thoughtlessly,

•  contemptuously,

•  disdainfully,

•  disrespectfully,

•  impolitely,

•  rudely,

•  scornfully,

•  snootily,

•  cruelly,

•  heartlessly,

•  nastily,

•  viciously,

•  shabbily,

•  unfairly

1: according to the rules of logic;

  * e.g., " ... your argument isn't valid because you're taking what should be the conclusion and using it as a premise "

•  Synonyms : 

•  analytic,

•  coherent,

•  consequent,

•  good,

•  logical,

•  rational,

•  reasonable,

•  sensible,

•  sound,

•  well-founded,

•  well-grounded

•  Antonyms : 

•  illegitimate,

•  illogical,

•  incoherent,

•  inconsequent,

•  inconsequential,

•  invalid,

•  irrational,

•  unreasonable,

•  unsound,

•  weak

2: based on sound reasoning or information;

  * e.g., " ... only further investigation will show whether your theory is valid "

•  Synonyms : 

•  commonsense,

•  commonsensible,

•  commonsensical,

•  firm,

•  good,

•  hard,

•  informed,

•  just,

•  justified,

•  levelheaded,

•  logical,

•  rational,

•  reasonable,

•  reasoned,

•  sensible,

•  sober,

•  solid,

•  well-founded

•  Antonyms : 

•  groundless,

•  illogical,

•  invalid,

•  irrational,

•  nonrational,

•  nonsensical,

•  nonvalid,

•  unfounded,

•  uninformed,

•  unjustified,

•  unreasonable,

•  unreasoned,

•  unsound