argumentum ad populum

Latin: argūmentum (“argument”, “proof”) + ad (“to”, “toward”) + populum (accusative singular of populus, “people”, “nation”) ≈ “appeal to the people”

• (Classical) IPA^(key): /aɹ.ɡuːˈmen.tum ad ˈpo.pu.lum/, [aɹ.ɡuːˈmen.tũ ad ˈpo.pu.lũ]
• (Received Pronunciation) enPR: ärgyo͞omĕnʹtəm ăd pŏʹpyo͝oləm, IPA^(key): /ɑːɡjuːˈmɛntəm æd ˈpɒpjʊləm/

argumentum ad populum (plural argumenta ad populum)

1. (rhetoric) A fallacious argument that concludes a proposition to be true because many or all people believe it; it alleges that “if many believe so, it is so”.
   • 2001, Martin Reisigl and Ruth Wodak, Discourse and Discrimination: Rhetorics of Racism and Antisemitism‎, page 166:

     The appeals to the public were also expressed differently: that is to say, much less by fallacious argumenta ad populum that played on the fears of the addressees, than by an appeal to rational insights, humanity and democracy.

• (“if many believe so, it is so”): argumentum ad numerum, bandwagon fallacy