As another way of expressing the idea of thick libertarianism, Gary Chartier draws a nice distinction between the libertarian principle and the libertarian ideal:
A libertarian, I take it, is someone who is for liberty and against aggression. The libertarian doesn’lt like to be pushed around, and doesnt like to see other people pushed around, either. The libertarian will likely affirm some version of what I will call the libertarian principle, and will have good reason as well to embrace the libertarian ideal.
In its strongest form, the libertarian principle holds that someone may rightly use force against the person or property of another only to prevent or end an unjust attack or to secure compensation for the damage done by such an attack. On weaker versions, the initiation of force, while infrequently permissible, must meet very demanding requirements.
The libertarian ideal calls for real freedom in all aspects of life. The libertarian need not, and likely will not, suppose that just any action that does not involve the misuse of force is morally reasonable. Conduct that is not aggressive can, and frequently does, amount to the mistreatment of others. Often, this mistreatment will reduce their freedom to make choices about their own lives. Someone motivated by the libertarian ideal will challenge such mistreatment even while granting that it may be narrowly consistent with the libertarian principle and may not reasonably be met with the use of force.