The Twelve Nidanas have twofold cause and effect, but they are divided into three phases rather than just past and future life.

Regarding the twofold cause and effect, the first is termed that which “causes” and “to be caused.” Here, “cause” refers to inducing the five aggregates of the future life. In other words, without the preceding cause and condition, the subsequent cause and condition or the next link will not come about. The latter, the one “to be caused,” is the cause and condition brought by the one that “causes.”

The second is termed that which “generates” and “to be generated.” It means that if there was nothing to generate, the five aggregates of the future life would never be formed or generated. The cause is the one “generates” and the effect is the one “to be generated”.

~ Depicted from THE RIGHT VIEW : The Twelve Nidanas—the sequence of cyclic existence