How did an assisted ready-made differ from a pure ready-made for Marcel Duchamp?

For Marcel Duchamp, the distinction between these two types of ready-made lies in the level of the artist's physical intervention:

• Pure ready-made: This consists of a single, mass-produced, commonplace object selected by the artist and designated as art, such as his Bottle Rack or the famous urinal titled Fountain.1
• Assisted ready-made: This involves the artist intervening by combining two or more objects to create a new work. An example is his first ready-made, Bicycle Wheel, which featured a wheel mounted on a stool.1

By utilizing these objects, Duchamp sought to challenge the traditional emphasis on the uniqueness of art, shifting the definition of art from a material process to an intellectual one.1