In relation to what appear as physical objects it is us who are the contingent or variable element; even if the object is fleeting it is us, via our attention, who come and go. The relation prescribes the roles.
The difference, in order to be a difference, must be intelligible and therefore must arise in a field of intelligence. One might seek to gain insight into such a field, what is it, how does it work, why is it, and so on, but can such inquiry make any sense at all, since it would seek to penetrate into the unintelligible, the unknowing? Absurd hubris of the knowing reflex that feels that it is entitled to go anywhere, to reduce any question to its own terms of reference. Content yourself with special investigations into concrete matters, physical and mental, and the modes of their relations. There are then at least three distinct registers to consider.  First is the phenomenological descriptive, as when one carefully details, in an objective tone of voice the components of an event, the objective tone being the tone of greatest generality. Next the poetic allusive, as when the event in its specificity is located in an open-ended field of associations, allusions and meanings, and becomes freighted with subjective meanings; paradoxically, these communicate more directly than the objective. The third is the register of the miraculous, in which the object, any objects, conveys its particular and general quality of silence, beyond all meanings, beyond all need to communicate.