Where we have insufficient information to reach a conclusion, we consider as possible any theory which has evidence to support it, while rejecting any that have no evidence or which contradict known evidence.
PD 24: “If you reject absolutely any single sensation without stopping to distinguish between opinion about things awaiting confirmation and that which is already confirmed to be present, whether in sensation or in feelings or in any application of intellect to the presentations, you will confuse the rest of your sensations by your groundless opinion and so you will reject every standard of truth. If in your ideas based upon opinion you hastily affirm as true all that awaits confirmation as well as that which does not, you will not avoid error, as you will be maintaining the entire basis for doubt in every judgment between correct and incorrect opinion.”
Epicurus' Letter to Pythocles: “For in the study of nature we must not conform to empty assumptions and arbitrary laws, but follow the promptings of the facts; for our life has no need of unreason and false opinion; our one need is untroubled existence. All things go on uninterruptedly, if all be explained by the method of plurality of causes in conformity with the facts, so soon as we duly understand what may be plausibly alleged respecting them. But when we pick and choose among them, rejecting one equally consistent with the phenomena, we clearly fall away from the study of nature altogether and tumble into myth. Some phenomena within our experience afford evidence by which we may interpret what goes on in the heavens. We see how the former really take place, but not how the celestial phenomena take place, for their occurrence may possibly be due to a variety of causes. However, we must observe each fact as presented, and further separate from it all the facts presented along with it, the occurrence of which from various causes is not contradicted by facts within our experience.”