Antinomy

which Merriam-Webster defines as:

A contradiction between two apparently equally valid principles or between inferences correctly drawn from such principles

and of which Britannica states

...contradiction, real or apparent, between two principles or conclusions, both of which seem equally justified;

Antinomy

which Merriam-Webster defines as:

A contradiction between two apparently equally valid principles or between inferences correctly drawn from such principles

and of which Britannica states

...contradiction, real or apparent, between two principles or conclusions, both of which seem equally justified;

Not to be confused with antimony, chemical element #51.

Antinomy (Greek ἀντί, antí, "against, in opposition to," and νόμος, nómos, "law") refers to a real or apparent mutual incompatibility of two laws, beliefs, or conclusions.

Antinomy

which Merriam-Webster defines as:

A contradiction between two apparently equally valid principles or between inferences correctly drawn from such principles

and of which Britannica states

...contradiction, real or apparent, between two principles or conclusions, both of which seem equally justified;