perceptive vs perceptiveness

perceptive is not a noun while perceptiveness is a noun.

Word	Noun	Adjective	Verb	Adverb
perceptive	No	Yes	No	No
perceptiveness	Yes	No	No	No

perceptive (noun)	perceptiveness (noun)
	the quality of insight and sympathetic understanding
	delicate discrimination (especially of esthetic values)
	perception of that which is obscure
	a feeling of understanding

perceptive (adjective)	perceptiveness (adjective)
having the ability to perceive or understand; keen in discernment
of or relating to perception