From Richard Serra’s 2006 interview with Kynaston McShine, published in MOMA’s Richard Serra Sculpture: 40 Years:
One of the first things I did when I started working in New York was to write down a list of verbs — to splash, to tear, to roll, to cut, and so on. I then enacted those verbs in the studio with rubber and lead in relation to time and place. The residues of the activities didn’t always qualify as art. I was primarily interested in the process and it was important that whatever was finally made reveal its making. Some of the residues were so replete in their exploration of material and the simplicity and singularity of the process that they would go unquestioned. Anyone could reconstruct their making. Some of them took on what I thought was sculptural form. For instance, enacting the verb “to lift” I took a rectilinear sheet of rubber lying flat on the floor, grabbed it from its edge on one side in the center, and lifted it up. When you lift the rubber sheet, it free-stands and makes an interior and an exterior space with a continuous topological surface. To simply have lifted a sheet of rubber and made a sculptural form was satisfying in and of itself. Of course I also worked through a lot of verbs that remained activities and nothing more. The verb list allowed me to experiment without any preconceived idea about what I was going to make and not worry about the history of the sculpture. I wasn’t burdened by any pre-scripted definition of material, process, or end product.