 This gives us the basic application of the barrier doctrine: the fact that God is a physical thing cannot explain God’s nature as a thinking thing; nor is explanation possible in the other direction. But the barrier doctrine also extends to creaturely intentions, sensations, and movements. Ontologically, all the things familiar to us from ordinary experience – animals, plants, inanimate objects – are for Spinoza merely modifications or “modes” of the single substance, “ways [modis]” that God is, just as (to borrow examples from Lin 2018) a wrinkle in a rug is one way a rug can be, and a fist one way a hand can be. Spinoza explicitly applies the barrier doctrine also to modes, stating that no modification of the thinking substance can require for its explanation the concept extension, and no modification of the extended substance can require for its explanation the concept thought: