Radium atoms decay by emitting alpha particles at random. Are these events without cause?
Of course one may take a closer look at radium nuclei to determine a possible reason why they decay; for example a hidden-variables model of QM may provide an explanation.
But the essential question I'm driving at is this: if random events occur in nature are they then by definition without cause? (The above example being simply a concrete illustration).
example: If we find a particular atom decays, and we later find out that its a Radium atom - we could say it decays because it is a Radium atom. In fact this is a tautological statement. We still haven't found the cause.
If an event is determined by its circumstances, only that event occurs and no other. If its undetermined by circumstances, then given something must happen, a range of possible events present themselves. Either all occurs, or one of these possible events occur and this choice must be taken at random, ( for if not, it is determined, and we're not interested in this case here).
An epistemologicaly random event is one which has only the appearance of randomness, given more precise knowledge of the events circumstances, one can determine why this event occurs as opposed to another. For example, a dice throw given Newtonian Mechanics is such an event. If one could precisely know how the dice is thrown and thus model its trajectory one can explain why a five occurs rather than a six.
An ontologically random event is one which knowledge of circumstances is not a barrier; it is random by fiat. In principle completely precise knowledge of circumstances will not enable prediction in a precise sense (a statistical prediction is still possible).