If you genuinely believe something to be true but it is, in fact, false, it can still be considered a lie in a subjective sense. However, the lie is not intentional or malicious in this case, but rather a result of a mistaken belief or a misconception.
A lie, traditionally defined, involves deliberately and knowingly providing false information with the intention to deceive others. In that strict sense, if you genuinely believe what you are saying, it wouldn't be considered a lie since there is no intent to deceive.
However, there is a concept known as a "lie of omission" or a "lying by telling the truth," which occurs when someone withholds important information or presents partial truths to create a misleading impression. In such cases, even though the information provided may be true, the intent to mislead can still be seen as deceptive.
It's essential to differentiate between someone who genuinely believes something to be true (even if it's false) and someone who knowingly presents false information with the intent to deceive. The former may be misguided or misinformed, but their communication is not intentionally deceitful, while the latter is intentionally trying to mislead others. Context, intent, and awareness of the truth are crucial factors in determining whether something can be labeled as a lie or not.