Property "of another" means a building or other property, whether real or personal, in which a person other than the offender has an interest which the offender has no authority to defeat or impair, even though the offender may also have an interest in the building or property.
Arson is a Class 2 felony. Residential arson or place of worship arson is a Class 1 felony.
720 ILCS 5/20-1