 Positive conceivability amounts to coherently imagining a scenario in which something is the case. The aim is to “form some sort of clear and distinct conception of a situation in which the hypothesis is true” (Chalmers 2010: 144). It need not be a complete description of a scenario, but it must be sufficiently detailed so as to verify the statement being considered. By contrast, negative conceivability is the inability to a priori rule out a certain scenario. That is, negative conceivability amounts to one’s inability to rule out a possibility as incoherent based on what one knows. This is often weaker than positive conceivability, since it often derives from ignorance of the relevant facts. For example, if one does not know that water is H2O, they may find the statement “water might not contain hydrogen” conceivable because they cannot rule out the statement as a priori incoherent. Conceiving of water without hydrogen in the positive sense, on the other hand, requires constructing a scenario in which water is present without hydrogen at the relevant depth of detail required to verify the claim. Arguably, that sort of scenario cannot be constructed once one knows the relevant empirical facts, since if they are attentively engaged in the construction they will notice a contradiction between water being H2O and hydrogen being absent.