Instrumental causes for karma coming into effect

The living being is said to experience, without any effort, the fruit of the merit and sin earned by its own karma, and the aggravation and calming of vata, pitta and the other doshas are the instrumental causes through which sin and merit bear fruit. A footnote adds that merit brings happiness and sin brings sorrow, the calming of the doshas being the instrumental cause for merit and their aggravation the cause for sin.