different between weightiness vs cogency

English

Etymology

weighty +? -ness

Noun

weightiness (usually uncountable, plural weightinesses)

1. The quality of being weighty.

English

Noun

cogency (countable and uncountable, plural cogencies)

1. The state of being cogent; the characteristic or quality of being reasonable and persuasive.
   • 1781, Samuel Johnson, "Addison," in Prefaces, Biographical and Critical, to the Works of the English Poets, J. Nichols (London), vol. 5, page 156:

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

   • 1928, Richard McKeon, "Thomas Aquinas' Doctrine of Knowledge and Its Historical Setting," Speculum, vol. 3, no. 4 (Oct), page 444:

     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.

References

• Webster, Noah (1828) , “cogency”, in An American Dictionary of the English Language
• cogency in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.
• “cogency” in Dictionary.com Unabridged, Dictionary.com, LLC, 1995–present.
• Oxford English Dictionary, second edition (1989)
• Random House Webster's Unabridged Electronic Dictionary (1987-1996)