720 ILCS 5/1-2

The provisions of this Code shall be construed in accordance with the general purposes hereof, to: (a) Forbid and prevent the commission of offenses; (b) Define adequately the act and mental state which constitute each offense, and limit the condemnation of conduct as criminal when it is without fault; (c) Prescribe penalties which are proportionate to the seriousness of offenses and which permit recognition of differences in rehabilitation possibilities among individual offenders; (d) Prevent arbitrary or oppressive treatment of persons accused or convicted of offenses.