This is the secret of General Miaow.
In one sense, this secret points to the anomalies that invariably confound any understanding of anything. Anyone who thinks they have the world figgered out is met with events of high credibility and high strangeness that their system is completely unable to explain. Newtonian physics was confounded by relativity. Mechanistic worldviews that ignore consciousness are confounded by such things as extra-sensory perception (as evidenced by reproducable, randomised tests) and the placebo effect. the double slit experiment seems to suggest the perspectival nature of the physical world. quantum events seem not to be causally determined. cryptozoology, ufo reports and other forteana provide evidence too compelling for the rational person to ignore, and too weird for the rational person to understand.
So. Impossible things keep happening.
it could also refer to the fundamental possibility of nihilism. it can be read much like the maxim 'nothing is true; everything is permitted'. There is no absolute fact, no 'truth with a capital T', therefore we live not in reality but in consciousness. There are no things, facts, laws, necessities or truisms, only experiences, sensations, ideas, perspectives and vicissitudes.