 Enduring products last longer than the action which produces them; they originate from a transformation or a rearrangement of pre-existing physical material in the course of the action: footprints in the sand are enduring products arising from the change of configuration of grains of sand (the material) as a product of the action of walking applied to that material (Twardowski points out that the product is not the grains of sand arranged in some way, but the arrangement itself, §26). If actions are processes, non-enduring products are events whereas enduring products present themselves as things (§ 27). Among enduring products, we find physical products (such as footprints in the sand) and psychophysical products (such as paintings). A mental product, such as a judgment, is never enduring (§29), but it can have its expression in an enduring psychophysical product, such as a written sentence. 