If you want to understand today’s Democratic Party, a word search of the Democrats’ debate last week provides a pretty clear picture.

Here is how many times key words were spoken:

Wall Street: 23

Tax: 20

Inequality: 9

Wealthy: 7

Now, compare the number of times other national concerns were mentioned:

ISIS: 4

Terror/ists/ism: 2

Defense: 2

Military (excluding Jim Webb): 1

Freedom: 1

Debt (national): 0

Liberty: 0

Strength: 0

Armed forces: 0

Islamist/Islamic: 0

Material inequality is the predominant concern of the Democratic Party. Indeed, material inequality has been the predominant concern of the left since Karl Marx.

This raises two questions:

How important is material inequality?

And if it is not that important, why does it preoccupy the left-wing mind?

The answer to the first question is: It depends.

It depends, first of all, on the economic status of the poorer members of the society. If the bottom percentile society has its basic material needs met, then the existence of a big gap between its members and the wealthiest members of the society is not a moral problem.

But if the members of the bottom rung of society are in such an impoverished state that their basic material needs are not met, and yet there is a supremely wealthy class in the same society, then the suffering of its poorest class renders that society’s inequality a moral problem.

And what most matters in both cases is whether the wealthiest class has attained its wealth honestly or corruptly. If the wealthy have attained their wealth morally and legally, then the income gap is not a moral problem.

In a free society, wealth is not a pie — meaning that when a slice of pie is removed, there is less of the pie remaining. And the poorer members of society have the ability to improve their economic lot. Through hard work, self-discipline, marriage and education — and with some degree of good luck — the poor can join the middle class and even the wealthy class.

The latter is generally the case in America. Unlike in most societies, for most Americans being poor is not a fate. The only time being poor becomes permanent is when noneconomic factors render it so. These factors include not having a father in one’s life, growing up with no family or social emphasis on education, women having children without a man, and men having children without committing to the mother of those children.