They labeled these three dimensions activity , evaluation , and potency . They called this general theory of meaning the semantic differential . Their theory essentially states that you can rate any object along those three dimensions. If you like the ballet, you would probably rate it high on activity, favorable on evaluation, and powerful on potency. The theorists who came up with the idea of the semantic differential thought that the meaning of any concepts could be described well by rating the concept on these three dimensions.
Unidimensional concepts are generally easier to understand.
You have either more or less of it, and that's all. You're either taller or shorter, heavier or lighter. It's also important to understand what a unidimensional scale is as a foundation for comprehending the more complex multidimensional concepts. But the best reason to use unidimensional scaling is because you believe the concept you are measuring really is unidimensional in reality. But, if the concept you are studying is in fact multidimensional in nature, a unidimensional scale or number line won't describe it well.