Paul L. Anderson, a prolific contemporary promoter of pictorialism, advised his readers that true art photography conveyed "suggestion and mystery", in which "mystery consists in affording an opportunity for the exercise of the imagination, whereas suggestion involves stimulating the imagination by direct or indirect means." Science, pictorialists contended, might answer a demand for truthful information, but art must respond to the human need for stimulation of the senses. This could only be done by creating a mark of individuality for each image and, ideally, each print.