“Human is a species” is natural because the assertion concerns the universal nature. “Humanity is in loss” is indefinite because the assertion relates to humans but leaves the scope of its individuals unstated.
Natural: a claim about the nature itself.
Indefinite: a claim about the nature's instances with no expressed quantity.
The distinction is not determined by the word “human” or its definite article. What matters is what the judgment is predicated of.
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Categorical Propositions: Singular, Natural, Quantified and Indefinite Forms
“Human is a species” is natural because the assertion concerns the universal nature. “Humanity is in loss” is indefinite because the assertion relates to humans but leaves the scope of its individuals unstated.
Natural: a claim about the nature itself.
Indefinite: a claim about the nature's instances with no expressed quantity.
The distinction is not determined by the word “human” or its definite article. What matters is what the judgment is predicated of.