It's the same answer. God cannot be a demon, because truth cannot be a lie. God cannot be a demon because goodness can't be evil.

Second, it's the same answer: we evaluate character by motives, behavior, and attitudes. We assess the character of God by what the Bible says, and so we can tell he is not some demon. By logic, revelation, and experience, we can conclude that God is good.

If God were a demon, He couldn't be God. If God were immoral in any way, He couldn't be God. If God could lie, He couldn't also be God. If God were unjust, He couldn't be God. These are self-contradictory concepts and definitions. It's like asking, "How do you know that a circle is really round and not really a square"?

If we want to know if God is really God and not some demon, we define "God" and "demon," then we look at the characteristics of God and the characteristics of demons, and then we assess which definition and category YHWH fits into.

I'm not asking "how do you know God is good/truthful?" I'm asking "how do you know this entity that calls itself 'Jehovah/Yahweh' and that you worship is really God and not some demon?"

First, that's not really a lot of words.

Second, I did actually answer the question.

Third, you [i]can[/i] say the same thing about anyone who makes a claim. The rules are the same for everyone. When another god makes the same claim, you weigh the evidences to determine truth. It's the same in science, history, law, politics, economics, psychology, or anything else. We tell someone's character by their attitudes, thoughts, and actions, and we assess their nature by those criteria. We use our brains and be as wise as we can. That's how we know we can trust the being who wrote the Bible, and we know we can't trust the source of the other religious works (the Qur'an and the Bhagavad Gita, for instance. We put everything we know on the table and assess it by rational criteria. So I did actually answer.

And as to the second part, it would be self-contradictory and impossible for a true God to lie. He/She/it would not be a true God if it were true that God were false (you can read even in this sentence the impossibility of it: "if it were true that it was false, and conversely false that it was true." Duh. That just can't be so.

Why can't I say the same thing about any other god that claims the same thing? I feel like you wrote a lot of words, but didn't actually answer.

We tell someone's character by their attitudes, thoughts, and actions. We can assess the actions of malicious/evil spirits by the harm they do. We can assess the character of God by the thoughts, motives, and actions that are told to us in the Bible and that we see in history. We can use our brains to their fullest capacity.

It would be a contradiction in terms and ontology if God could lie or were evil, and therefore it's impossible.

1. God is ideally definable as the ideal being, greater than any other imaginable being, and perfect in his attributes. Therefore if God could lie, he could not be God, and so a self-defeating and self-contradictory proposition.

2. Without truth, there is no morality. Without morality, there is no goodness or right/wrong. Without the possibilities of truth, goodness, or right, there can be no God. It goes against every reasonable and acceptable definition of God.

3. The Liar's Paradox (https://en.wikipedia.org/wiki/Liar_paradox) shows that if God is a liar, he is a living ontological contradiction, which is logically impossible. A cannot equal non-A.

There is a Christian belief (not saying it's one all Christians do hold or have held, just that it has been held) that many or all pagan/false gods are actually malicious/evil spirits. I tend to be sympathetic towards this idea. But I can't help but extend it to Christianity itself.

There is this supernatural being that inspired the books of the Bible but how can I trust that this entity is really who he says he is, the one creator god, all good and all powerful and all that, and not just another lying evil spirit?