vagueness; Vaihinger Hans; valid; valid - invalid; validity; Valla Lorenzo; value; variable; Veblen Thorsten; vector; vector space; Venn John; Venn diagrams; verbal dispute; verecundiam - argumentum ad; verifiability principle; verification; veritas; vernunft; Verstehen; vice; Vico Giambattista; Vienna Circle; virtual; virtual reality; virtue; virtue ethics; virus; visualisation; vitalism; voice recognition; volition; voluntarism; Voltaire - Francois Marie Arouet; voluntarism; voluntary - involuntary; von Neumann integer; von Neumann John; von Neumann ordinal; voting paradox;