P9: The idea of a singular thing which actually exists has God/Nature for a cause not insofar as he is infinite, but insofar as he is considered to be affected by another idea of a singular thing which actually exists; and of this {idea} God/Nature is also the cause, insofar as he is affected by another third {NS: idea}, and so on, to infinity.

Dem.: The idea of a singular thing which actually exists is a singular mode of thinking, and distinct from the others (by P8 C and P8 S), and so (by P6) has God/Nature for a cause only insofar as he is a thinking thing. But not (by IP28) insofar as he is a thing thinking absolutely;18 rather insofar as he is considered to be affected by another {NS: determinate} mode of thinking. And God/Nature is also the cause of this mode, insofar as he is affected by another {NS: determinate mode of thinking}, and so on, to infinity. But the order and connection of ideas (by P7) is the same as the order and connection of causes. Therefore, the cause of one singular idea is another idea, or God/Nature, insofar as he is considered to be affected by another idea; and of this also {God/Nature is the cause}, insofar as he is affected by another, and so on, to infinity, q.e.d.

Cor.: Whatever happens in the singular object of any idea, there is knowledge of it in God/Nature, only insofar as he has the idea of the same object.

Dem.: Whatever happens in the object of any idea, there is an idea of it in God/Nature (by P3), not insofar as he is infinite, but insofar as he is considered to be affected by another idea of {NS: an existing} singular thing (by P9); but the order and connection of ideas (by P7) is the same as the order and connection of things; therefore, knowledge of what happens in a singular object will be in God/Nature only insofar as he has the idea of the same object, q.e.d.