Is “positivity” a real word?

A reader questions the acceptability of the word positivity:

Is “positivity” a real word? I have found it on a couple of on-line dictionary sources, but it sounds so wrong and makes me cringe every time I hear it. I feel that people think that if negativity is a word, then the antonym must be positivity, and not positiveness.

Until I received this query I’d never questioned the reality of the word positivity. Afterwards I discovered that the question appears to be a common one on the Web. I don’t understand why this should be so.

The suffix -ivity occurs in a great many common English words. A few of the most familiar:

activity
captivity
conductivity
creativity
festivity
sensitivity
nativity
negativity
objectivity
receptivity

The suffix -ivity is added to an adjective to make it into an abstract noun. The suffix appears in borrowings and adaptations of Latin and French words from the end of the Old English period; it becomes common after the Norman Conquest: nativity (1225), captivity (1380). When the adjective ends in -il or -le, the suffix -ility is added to the adjective: humility (1315), durability (1374), ability (1398).

The suffix -ness is the more usual suffix used to form abstract nouns nowadays, but -ivity is still used in scientific contexts to form abstract nouns denoting a specific property of a material: incendivity, elastivity.
According to the OED, positivity predates negativity in English by 167 years. In 1659, the reference is to the “positivity of sin”; in 1826, Coleridge speaks of the “Spirit of Negativity.”

The reader quoted above feels that positiveness is the “real” word and that positivity should not be used at all. Many speakers do use the word positiveness to mean the quality of looking on the bright side, but others see a difference in connotation between positivity and positiveness.
For speakers who see a difference, positivity means the quality of looking on the bright side:

If you approach the day with enthusiasm, positivity and openness, usually you’ll get the same back.

Positiveness, on the other hand, is seen by some as a synonym for dogmatism:

These relations are so extensive, that positiveness, or dogma, is scarcely anywhere free from the liability to contradiction.

As far as I can tell, there’s no reason to despise the word positivity.
According to the Google Ngram Viewer, positivity is far more common in print than positiveness. Indeed, every example of the word positiveness in the Word file of this article has a red line under it.

Source: Daily Writing Tips