According to an instrumental theory, the act of terrorism is an intentional choice by a political actor. The organization as a unit acts to achieve collective values which involve radical changes in political and social conditions. Terrorism is interpreted as a response to external stimuli, particularly government actions. An increase in the cost or a decrease in the reward for violence will decrease the likelihood of violence. The second explanation focuses on internal organizational processes of the terrorist group or among organizations sharing similar objectives. Terrorism is explained in terms of the organization's struggle for survival, usually within a competitive environment. Leaders ensure organizational maintenance by offering varied incentives to followers. Leaders seek to prevent both defection and dissent by developing intense loyalties among group members. The organization responds to pressure from outside by changing the incentives offered to members or through innovation. Both of these theories offer approaches to understanding terrorism that have policy implications, and both have some empirical foundation. It may be that a combination of the two theories is needed to analyze terrorist actions, or it is possible that some terrorist organizations more closely fit the strategic theory, while others are more powerfully influenced by organizational politics. 29 footnotes.