a. An adjective pronoun usually agrees with an appositive or predicate noun, if there be one, rather than with the word to which it refers (cf. § 306):—
“hīc locus est ūnus quō perfugiant; hīc portus, haec arx, haec āra sociōrum ” (Verr. 5.126) , this is the only place to which they can flee for refuge; this is the haven, this the citadel, this the altar of the allies.
“rērum caput hōc erat, hīc fōns ” (Hor. Ep. 1.17.45) , this was the head of things, this the source.
“ eam sapientiam interpretantur quam adhūc mortālis nēmō est cōnsecūtus [for id...quod] ” (Lael. 18) , they explain that [thing] to be wisdom which no man ever yet attained.
A&G, sectio centum quadraginta sex, wrote:146. The Demonstrative Pronouns are used to point out or designate a person or thing for special attention, either with nouns as Adjectives or alone as Pronouns. They are:—hīc, this; is, ille , iste, that; with the Intensive ipse, self, and īdem, same;