speculative
Meaning: not based in fact
Usage: Sadly, Tessa was convicted on merely speculative evidence.
credulity
Meaning: readiness to believe
Usage: His credulity made him an easy target for con men.
plausible
Meaning: believable, reasonable
Usage: He studied all the data and then came up with a plausible theory that took all factors into account.
agnostic
Meaning: believing that the existence of God cannot be proven or disproven
Usage: Joey’s parents are very religious, but he is agnostic.
hypothetical
Meaning: supposed or assumed true, but unproven
Usage: The teacher asked a hypothetical question about what would happen if gravity suddenly disappeared.