Originally Posted by
Occam's Banana
A "thin" libertarian is one who thinks that libertarian theory should be kept as minimal (and hence, as "thin") as possible. This is to be done by restricting the body of libertarian theory itself to the most basic and fewest necessary axioms, along with the "theorems" (such as the Non-Aggression Principle) which can be derived from that minimal set of basic axioms.
A "thick" libertarian, on the other hand, is one who thinks that libertarian theory should be expanded (and hence, "thickened") to formally include things like opposition to racism and support for "equality" (whatever that might mean).
For example, a "thin" libertarian may hate and denounce racism and will, of course, oppose racist policies that violate the NAP. But as a libertarian, he will oppose such racist policies as "unlibertarian" because they violate the NAP - not because they are racist. He might also oppose racist policies that do not violate the NAP because they are racist, but he will consider his opposition to them to be separate from his identity as a libertarian. He is willing to consider NAP-supporting racists to be libertarians, despite the fact that they are racists.
A "thick" libertarian, on the other hand, will insist that in order to be libertarian one must always hate and denounce racism and racist ideas and attitudes. As a libertarian, he will oppose any and all racist policies as "unlibertarian" regardless of whether they violate the NAP - because they are racist. He will consider his opposition to them to be part of his identity as a libertarian. He is not willing to consider NAP-supporting racists to be libertarians, because of the fact that they are racists.
"Thick" libertarians tend to be of the leftist variety, and some of them even support things like "universal basic income" in the name of "equality."