If a living entity were subject to the results of his previous activities there would be no scope for free will.

“The argument may be given that if a living entity were subject to the results of his previous activities there would be no scope for free will; once having committed a sinful action, the living entity would be bound in an endless chain of suffering, being perpetually subject to previous reactions. According to this speculation there cannot be a just and omniscient God, since the living entity is forced to commit sinful activities by the reactions of his previous activities, which were reactions to still previous activities. Since even an ordinary gentleman will not unfairly punish an innocent person, how could there be a God witnessing the helpless suffering of the conditioned souls within this world?

This foolish argument can easily be refuted by a practical example. If I purchase a ticket for an airline flight, board the plane and commence the flight, once the plane has taken off my decision to board the plane forces me to continue flying until the plane lands. But although I am forced to accept the reaction of this decision, on board the plane I have many new decisions I can make. I may accept the food and drink from the stewardesses or reject it, I may read a magazine or newspaper, I may sleep, walk up and down the aisle, converse with other passengers, and so on. In other words, although the general context — flying to a particular city — is forcibly imposed upon me as a reaction to my previous decision to board the plane, even within that situation I am constantly making new decisions and creating new reactions. For example, if I cause a disturbance on the airplane I may be arrested when the plane lands. On the other hand, if I make friends with a businessman sitting next to me on the plane, such a contact may lead to a favorable business transaction in the future.

Similarly, although the living entity is forced to accept a particular body by the laws of karma, within the human form of life there is always scope for free will and decision-making. Therefore the Supreme Personality of Godhead cannot be considered unjust for holding the living entity in human life responsible for his present activities despite the living entity’s undergoing the reactions of his previous work.”

Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Eleventh Canto, Chapter 03 – Text 06.