Tom rationalizes that his illicit use of marijuana is permissible because the drug is not particularly habit-forming and therefore should not be prohibited by law. tom's rationalization serves to

Tom's rationalization serves to reduce his cognitive dissonance
Cognitive dissonance refers to a situation where a person possess inconsistent belief, behavior, or personal opinion.
The consumption of marijuana usually impair our reasoning capabilities which make us more prone to cognitive dissonance.

Tom's rationalization serves to reduce his cognitive dissonance.
The concept cognitive dissonance was developed and introduced by the social psychologist Leon Festinger. It denotes situation involving conflicting attitudes, beliefs or behaviors that produces a feeling of discomfort. According Festinger we have an inner drive to hold all our attitudes and beliefs in balance.

The  ancient egyptians  who  built the pyramids  may have been  able  to move massive stone blocks across the desert by wetting the sand in front of a contraption  built  to pull the heavy objects