Definition of "contentful"

In answer to this question I want to propose that to is in fact always contentful—that it is never mere Case marking, strictly speaking—but that in certain contexts (namely, in V's headed by Dative-Shifting verbs) its grammatical contribution effectively "reduces" to Case marking and therefore can be suppressed under Passive.

1988, Richard K. Larson, On the Double Object Construction

Indeed, it seems to me that the special character of non-conceptually contentful perceptual states entails that all perceptual states contain non-conceptual content in this essentially distinct sense […] .

2007 October 25, Robert Hanna, “Kantian non-conceptualism”, in Philosophical Studies, volume 137, number 1

Can one have contentful but non-conceptual thought? My guess is that we can and I take it that my guess is buttressed by our ordinary practice of talking about the behaviour of animals and pre-linguistic children.

2011, Steven Hales, What Philosophy Can Tell You about Your Dog, Open Court, page 214

How contentful the whole life is of him, that neither deviseth mischief against others, nor suspects any to be contrived against himself.

a. 1678 (date written), Isaac Barrow, “(please specify the chapter name or sermon number). Of a Peaceable Temper”, in The Works of Dr. Isaac Barrow. […], volumes (please specify |volume=I to VII), London: A[braham] J[ohn] Valpy, […], published 1830–1831

With the setting sun sending long shadows loping ahead of them over the smooth hillocks of the downs, they came up with the lagoon; a contentful return home, with appetite brisked up by a ten-mile walk, and plenty of food to satisfy it.

1938, Norman Lindsay, Age of Consent, 1st Australian edition, Sydney, N.S.W.: Ure Smith, published 1962, page 63