Note: I use the words "value" and "goal" interchangeably in this post.

Terminal values are pursued for their own sake. Instrumental values are pursued as a means to attaining terminal values, or other instrumental values closer to the terminal values.

For example, if I had the ultimate goal of maximizing profit, I might break that up into the instrumental goals of increasing revenue and decreasing cost. Depending on the situation, those two instrumental goals can be broken up into even more specific instrumental sub-goals.

Instrumental sub-goals help to reduce repetition in thought. Conditions change in such a way as to change the actions demanded by an instrumental sub-goal, but not change the validity of the way in which the terminal goal is divided into sub-goals.

Irrationality is often caused by holding on to instrumental sub-goals even though they no longer serve your terminal goal. This is what Eliezer calls thought caching.

This came in the mail today:

Nominal - numbers are either the same or not

Ordinal - if different, one number is bigger than the other

Interval - differences in numbers can be compared

Ratio - zero is a significant point

The properties described are nested - nominality is needed for ordinality, which in turn is needed for interval-ality, in turn needed for ratio-ality.

Anything interval level and above is considered quantitative. Most qualitative measures serve only nominal function, i.e. whether something is the same or not.

More formally: http://en.wikipedia.org/wiki/Level_of_measurement [HT: Soo Mei]