"a supposition of an unknown support of qualities that are able to cause simple ideas in us." Without making a substratum, people would be at a loss as to how different qualities relate. Locke does, however, mention that this substratum is an unknown, relating it to the story of the world on the turtle's back and how the believers eventually had to concede that the turtle just rested on "something he knew not what". This is how the mind perceives all things and from which it can make ideas about them; it is entirely relative, but it does provide a "regularity and consistency to our ideas". Substance, overall, has two sets of qualities — those that define it, and those related to how we perceive it. These qualities rush to our minds, which must organize them. As a result, our mind creates a substratum (or substance) for these objects, into which it groups related qualities. Criticism of soul as substance Kant observed that the assertion of a spiritual soul as substance could be a synthetic proposition which, however, was unproved and completely arbitrary. Introspection does not reveal any diachronic substrate remaining unchanged throughout life. The temporal structure of consciousness is retentive-perceptive-prognostic. The selfhood arises as result of several informative flows: (1) signals from our own body; (2) retrieved memories and forecasts; (3) the affective load: dispositions and aversions; (4) reflections in other minds. Mental acts have the feature of appropriation: they are always attached to some pre-reflective consciousness. As visual perception is only possible from a definite point of view, so inner experience is given together with self-consciousness. The latter is not an autonomous mental act, but a formal way how the first person has their experience. From the pre-reflective consciousness, the person gains conviction of their existence. This conviction is immune to false reference. The concept of person is prior to the concepts of subject and body. The reflective self-consciousness is a conceptual and elaborate cognition. Selfhood is a self-constituting effigy, a task to be accomplished. Humans are incapable of comprising all their experience within the current state of consciousness; overlapping memories are critical for personal integrity. Appropriated experience can be recollected. At stage B, we remember the experience of stage A; at stage C, we may be aware of the mental acts of stage B. The idea of self-identity is enforced by the relatively slow changes of our