The great psychophysicist Gustav Theodore Fechner -- one of the foremost instigators of modern, scientific psychology -- wrote extensive speculations in a work called the Book of Life After Death which G. Stanley Hall describes thus: 

How now do the dead live on? First and chiefly in us. Fechner takes his leading concept from the mystic way in which Christ lives in his followers, who are members of his body and branches of his vine. To this larger life of his in the Church, his earthly career is only a grain of mustard seed. Gloriously his soul has gone marching on. Just so the dead press in upon us, yearning to add their strength to ours, for thus they not merely live, but grow. New impulsions and sudden insights in us are inspirations from them. Not only do the great and good dead influence and pervade us all the time, but we are exposed also to the bad. Many of them are always bad, and so if our will is weak and our personality unorganized, they may dominate us. Their visitation is insistent. They do not crave incarnation in the flesh, like Plato's spirits, but in our moral life, that therein they may be made perfect. We all have in us sparks from the lives of Luther, Goethe, Napoleon, etc., who think and act in us "no longer restrained by the limitations of the body, but poured forth upon the world which in their lifetime they moulded, gladdened, swayed, and by their personality they now supply us with influences which we never discern as coming from them." Each great dead soul extends itself into man and unites them in a spiritual organism. Thus, the dead converse wit each other in us. They also fight the good and bad in each other in us, causing strife in our souls.... 

There is, however, a higher soul in which we and all things live, move, and have our being, and in which and only in which spirits are real. We are, in fact, what we have become. The brain is a kind of seed which decays that the soul may live. The individual soul may mount on the collective souls of the dead as a sparrow is carried up on an eagle's back to heights it never could attain, but, when there, can fly off and even a little higher. At death the soul seems to drop below a threshold and the spark of consciousness might be conceived to go out but for the fact that the soul is not projected into an empty world but into one where it incessantly meets varying resistance that keep personality above the point of submergence or any other extinction without appeal to the conservation of energy. Just as attention moves about from point to point within the body, so after death the soul moves around the world. 

When the phenomena of spiritualism became popular in mid-nineteenth century Europe and America, Fechner sat with zeal at a number of seances. He was one of the few men of his age who, while not detecting trickery, had the depth of wisdom with which to incorporate but also transcend the sensationalism and trivia of the popular spiritualist impulse.