cogency

noun

1. (countable, uncountable)The state of being cogent; the characteristic or quality of being reasonable and persuasive.

   “All the enchantment of fancy, and all the cogency of argument, are employed to recommend to the reader his real interest.”

   “A philosophic study of the development of philosophies should be content to seek out the bases and cogencies of philosophies rather than engage upon a nostalgic search for sympathetic doctrines.”