Learn Portuguese (Portugal): Isto será apenas um engano?

In Portuguese, the Future Simple is often used to express uncertainty, probability, or a guess about the present. This is called the epistemic future. By asking Isto será...?, the speaker is wondering aloud, which translates naturally to 'Could this be...?' or 'I wonder if this is...?'

Could I use the conditional seria instead of será here?

Yes, but it changes the nuance. Isto seria apenas um engano? sounds more hypothetical, often translating to 'Would this just be a mistake?' Using the future será is the standard, most natural way to express a genuine present-tense doubt or conjecture.

What is the difference between um engano and um erro?

Both mean 'mistake', but engano often implies a misunderstanding, a mix-up, or a delusion (from the verb enganar, meaning to deceive or make a mistake). Erro is typically a factual or technical error, like a spelling mistake or a miscalculation. Here, um engano suggests a situational mix-up.

Why use the invariable pronoun Isto instead of Este?

Isto is used for abstract ideas, general situations, or unidentified things. Because the speaker is referring to the general situation ('this' whole scenario) rather than a specific masculine noun, Isto is required. If they were referring to a specific masculine object, like a report, they would use este.