At this point I shall permit myself to touch cursorily upon a theme which would deserve the most thorough treatment. The Kantian proposition that time and space are necessary modes of thought may be submitted to discussion to-day in the light of certain knowledge reached through psycho-analysis. We have found by experience that unconscious mental processes are in themselves ‘timeless’. That is to say to begin with: they are not arranged chronologically, time alters nothing in them, nor can the idea of time be applied to them. These are negative characteristics, which can be made plain only by instituting a comparison with conscious psychic processes. Our abstract conception of time seems rather to be derived wholly from the mode of functioning of the system W-Bw., and to correspond with a self-perception of it. In this mode of functioning of the system another form of protection against stimulation probably comes into play. I know that these statements sound very obscure, but I must confine myself to these few hints. So far we have got to the point that the living vesicle is equipped with a protection against stimuli from the outer world. Before that, we had decided that the cortical layer next to it must be differentiated as the organ for reception of external stimuli. But this sensitive layer (what is later the system Bw.) also receives excitations from within: the position of the system between outer and inner and the difference in the conditions under which this receptivity operates on the two sides become deciding factors for the functioning of the system and of the whole psychic apparatus. Towards the outer world there is a barrier against stimuli, and the mass of excitations coming up against it will take effect only on a reduced scale; towards what is within no protection against stimuli is possible, the excitations of the deeper layers pursue their way direct and in undiminished mass into the system, while certain characteristics of their course produce the series of pleasure-pain feelings. Naturally the excitations coming from within will, in conformity with their intensity and other qualitative characteristics (or possibly their amplitude), be more proportionate to the mode of operation of the system than the stimuli streaming in from the outer world. Two things are, however, decisively determined by these conditions: first the preponderance over all outer stimuli of the pleasure and ‘pain’ feelings, which are an index for processes within the mechanism; and secondly a shaping of behaviour towards such inner excitations as bring with them an overplus of ‘pain’. There will be a tendency to treat them as though they were acting not from within but from without, in order for it to be possible to apply against them the defensive measures of the barrier against stimuli (_Reizschutz_). This is the origin of projection, for which so important a part is reserved in the production of pathological states.