Sec.34 IPC requires active participation in action whereas Sec. 149 IPC. Common intention requires prior meeting of mind and unity of intention and overt act has been done in furtherance of the common intention of all. Common object may be formed without prior meeting of mind when the common object of the members of the unlawful assembly is one but intention of participants is different. It only requires that criminal act has been done in furtherance of common object. Section 34 is substantive evidence and other sections like 302 murder has to be clubbed with it. Section 149 is a constructive crime in itself. In section 34 Participation of the people in crime is an important aspect, even standing people who indirectly help in commissioning of crime are also prosecuted.