Our memories are private and particular; when you and I share an experience our experience is yet in the very moment of sharing different for you and for me, and our two memories of an event in the past are still more disparate. For memories are shaped and constrained by the deep-lying organic stress of what we have lived through, of our actual living, in the interval between then and now. A memory follows the solitary track of our individual experience, and, like the particle in modern Physical theory, is changed in and by the route it has traced.