The domain of existence is that which thought structures. This is not to say that thought creates the cosmos in any way, but that the term existence refers to the generalized structure or model that an awareness has created for itself. The process of thought's participation in the cosmos results in an awareness of certain forms and continuities whose domain is what is called existence. Within this existential environment, entities are said to exist. Existence is the ontological consequence of thought. All entities are on the cutting edge of existence where the certainty of ultimate oblivion is distributed by the random perturbations of nature.

This property of existing is attributed to a structure or form by an awareness abstracting it from perceptual experiences. To ascribe existence to an entity is to identify it as a one. Sufficient evidence needs to accumulate in the memory structures of the awareness, before any inductive processes can evaluate the probabilities as to the significance of the perceived form and hence the pragmatic decision to assume the existence or not of an entity.

Ranging from an almost universal agreement that the sun as an entity exists, thru the uncertainties about many biological species and physical particles, to the improbabilities of fairies and souls, attempted classifications of entities, as existing or not, will forever be subject to reappraisal. We recall that there was a mantis and a caterpillar on the swan plant barely minutes ago and now there is only a mantis. Perhaps the caterpillar was eaten by the mantis. We assume from the fossil record that dinosaurs have ceased to exist, yet there is always the haunting doubt, that perhaps there is a living example somewhere. The entity which we reassured ourselves existed a moment ago, may well not exist now, and the presumption of extinction has been premature on more than one occasion.

The most difficult phenomena in nature a self-awareness has to cope with, is that unexpected event whereby a familiar and valued entity, living or otherwise, ceases to exist. Many humans find this so incomprehensible, that an after-life is postulated, in an attempt to avoid the starkness of the reality.