the.com/naturalistic fallacy

means The mistake of concluding that because something is natural, it is therefore good, right, or how things ought to be.

from Coined by philosopher G.E. Moore in his 1903 book Principia Ethica, though he used it to name a slightly different slip — defining 'good' in terms of any natural property at all, like pleasure or desirability. The term later drifted into its more popular everyday use: the 'appeal to nature' blunder of treating 'natural' as a synonym for 'ethical.' David Hume had already flagged the deeper problem centuries earlier with his 'is-ought' gap, noting that no pile of facts about what IS can by itself tell you what OUGHT to be — Moore's phrase just gave that old logical gap a catchy name.