[tsimionescu]

> Nothing can exist without causality as we know it, i.e. a thing happens which is the cause of another thing that happens.

Not only is this not true of all conceivable worlds, it's not even true for the most commonly accepted explanation of physics. In the Copenhagen Interpretation of quantum mechanics, the value that will be observed in an experiment has no cause - it is random in some range. For example, if we detect an electron passing through the left slit of a double slit apparatus, there is no cause for why it passed through the left slit and not the right one (in the CI of QM).

[n4r9]

I guess CI admits a weaker form of causality, in which an effect produced according to a determined probability distribution. But even this is part of the map rather than the territory.

[tsimionescu]

Bit late, but I probably should have given virtual particles as a better example. Those are theorized to appear and disappear at random out of the void. Per the theory, there is no cause to this appearance (apart from it being permitted by the laws of physics).

Of course, this is ultimately a model and can be wrong. But my point is that we can definitely conceive of models of the world in which causality is not a strict requirement - and not just fantasy ones, but very concrete models with workable predictions.