What did Donald Trump do today?

He reminded everyone it's never his fault, specifically about the economy.

Faced with an economy slowed by his trade war, and fears of recession that have sent the stock markets plummeting, Trump took action today: he got on Twitter and said it was the media's fault.

While this was good for a few laughs online, there's a theme emerging in Trump's comments on the economy, besides the idea that nothing bad is ever his fault. Trump seems to believe that the world economy is a zero-sum game, where every transaction has a winner and a loser. He also tweeted this today:

In the real world, "as others falter," the United States economy gets weaker—which is exactly why even his own advisors were against launching unprovoked trade wars on countries the United States does a lot of business with. Individual business compete, but the overall economy tends to get stronger and weaker in unison. 

For example, when Trump managed to bankrupt four Atlantic City casinos at the height of that city's economic boom, it wasn't a windfall for his competitors. Instead, the debts he never paid and the vacant shells he left behind hurt the local economy. 

Trump has made a version of this basic mistake before. When he launched his trade wars more than a year and a half ago, he frequently talked about how the United States was somehow losing money when it had a trade deficit with another country. Of course, all it really means is that American consumers could afford to buy things from other countries.

Why should I care about this?

• The United States economy is way too important for the president to be this ignorant about it.

• Not every problem Donald Trump has can be blamed on the media.

• Having responsibility means taking responsibility.