Ayn Rand defined a concept as “a mental integration of two or more units which are isolated according to a specific characteristic(s) and united by a specific definition.” Really, though, most of the concepts in most people’s heads don’t live up to this standard. They’re often more like rough mental areas carved out by rather vague criteria. People do pretty well at concrete things like “person” and “rock,” but much less well with abstractions like “justice” and “beauty.” Ask people of different political views to define “terrorist” and see if they come up with coherent criteria, much less agree with each other.
Specific definitions aren’t the central point; they don’t dictate concepts. They can change as the relevant facts change. Twenty years ago, nearly everyone would have agreed that a book is a physical, printed object. Today we routinely apply the word to collections of bits. The change is reasonable; the content of a book is now often delivered as a collection of bits, and for many purposes it doesn’t matter whether we have the printed object or data in a computing device. The similarities are more important than the differences.
When definitions shift because people don’t have a clear idea of a concept’s distinguishing characteristics, though, it’s impossible to reason with any precision. What conclusions can you draw about terrorists as a class if you can’t say who is a terrorist and who isn’t? It becomes easy to draw different conclusions by changing criteria; if someone acting for a cause you support commits an act you’d otherwise call terrorist, your criteria might suddenly become much more restrictive. It’s not a conscious double standard but sloppy thinking.
It’s difficult to maintain full clarity on highly emotional issues, but developing good mental habits makes it easier. A key point is to ask yourself what conclusions you’d draw if certain things were different. Let’s say you support the threats by Boston’s Mayor Menino to ban Chick-Fi-A from the city because its president is against same-sex marriage. (This is hypothetical; I don’t suppose many people reading this blog do.) Would you also grant the right of mayors who oppose same-sex marriage to ban the sale of Kindles because Jeff Bezos has contributed to pro-legalization causes? A lot of inconsistencies are much subtler than this and harder to spot.
It’s a matter of ongoing mental exercise to treat concepts such as rights and freedom consistently regardless of our emotional responses to particular cases. When we don’t learn those habits, people can manipulate us easily.