Meaning is the subjective experience of this unity. Bion says that a particular fact illuminates an array of what had before been disjointed facts. He called this unifying principle the 'selected fact'. It is a mistake, however, to think of this as a fact such as a sensation which can never be unifying in the way he suggests. Psychological factors that have the same permeable quality as volume, weight, or density are grief, disappointment, longing, hope, despair, shame, goodness, or truth. It is a mental principle which infuses the sensual imagery. Grief, disappointment, hope, goodness, creativity, or truth are realities not ideas. So the 'all-inclusive principle' is as real as a stone or a crocodile but without physical characteristics. Freud refers to psychical reality though does not emphasise it. Freud implied that the relationship between the untransformed 'givens' and the coherent part of the personality is what produces the conflict that generates neurosis.