fallacy

As nouns the difference between fallacy and idea

is that fallacy is deceptive or false appearance; deceitfulness; that which misleads the eye or the mind; deception while idea is (philosophy) an abstract archetype of a given thing, compared to which real-life examples are seen as imperfect approximations; pure essence, as opposed to actual examples.

Fallacy is a see also of falsism.

As nouns the difference between fallacy and falsism

is that fallacy is deceptive or false appearance; deceitfulness; that which misleads the eye or the mind; deception while falsism is a claim that is self-evidently false, commonly used a rhetorical device.

As nouns the difference between fallacy and idolum

is that fallacy is deceptive or false appearance; deceitfulness; that which misleads the eye or the mind; deception while idolum is an insubstantial image; a spectre or phantom.