Let’s connect the dots between Donald Trump’s “tax plan”, his invitation to the murderous leader in Manila and saying he would be “honored” to meet with the dictator of North Korea. And let’s throw in his claim that Trumpcare will be better than Obamacare and that his skeletal tax plan would make him pay more.

While these facts might seem unrelated, each points to a fundamental truth about Trump that I have been trying to get people to understand since he announced his latest presidential campaign in June 2015: Trump doesn’t know anything.

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And Trump’s ignorance should scare you because the White House says he plans to fulfill all of his campaign promises – and among them is starting wars and using nuclear weapons.

Human beings have thousands of years of experience with taxes and diplomacy and yet Trump lives unaware of the basic principles of government finance and international relations.

Don’t take my word for it, even as someone who knows the man and has studied him closely for 29 years. Just listen to Trump’s own words. They show he acts like a classic con artist, all bluster and vagaries. He lives blissfully unaware of his ignorance of basic facts that anyone who paid attention in high school, much less college, should know.

Trump declared recently that Andrew Jackson was furious about the civil war even though he died 16 years before it began. Trump seems unaware Jackson was a slave-owning white supremacist.

Meeting with black leaders in February, Trump said that Frederick Douglass was “an example of somebody who’s done an amazing job and is being recognized more and more”.

That’s a neat trick for someone who was buried 122 years ago, not that Trump has a clue that Douglass was an abolitionist newspaper publisher, pastor and orator.

Trump is even ignorant about his tax plan, all 100 words of it, or that it violates principles of taxation articulated by Plato, Adam Smith and many other philosophers.

Trump said under his tax plan, he would pay more. Nope. He’d pay 86% less, based on his 2005 federal income tax filing, which I revealed in March at DCReport.org, the nonprofit news service I founded to track what Trump does, rather than tweets.

His tax wishlist would eliminate the Alternative Minimum Tax, a 1986 law signed by President Ronald Reagan. That law cost Trump nearly $31.3m of his $36.6m federal income tax bill in 2005.

Had Trump’s tax wishlist been in effect in 2005, he would have paid just $5.3m in federal income tax on an income of $152.7m.

That works out to slightly less than 3.5% of his income, which is lower than the effective income tax rate paid by the poorest half of American taxpayers that year. They paid slightly more than 3.5%. The difference is that Trump’s income was almost $3m a week while the poorer half got by on a tad more than $300 per week.

Then there’s geopolitics. Not only does Trump not know a Shia from a Sunni or the reasons it matters, he also came into office knowing nothing of the thousands of years of relations between China and Korea. Trump said Xi Jinping, the supreme leader in Communist China, schooled him during a recent telephone conversation.

What drives his praise for Rodrigo Duterte in the Philippines and Kim Jong-un in North Korea is his admiration for authoritarian rule.

What Trump does not grasp is that, by praising murderous dictators, he enhances their power at home and denigrates America’s standing as a beacon of individual liberty abroad.

Often Trump talks of his presidency in dictatorial terms, denouncing judges whose rulings he dislikes as “bad judges” and calling for a Congress that acts as a subordinate to the executive, rather than a co-equal branch of the American government. Few journalists point this out, however.

Trump has no idea what the constitution says are the duties, powers and limits on the president. Too bad no one asked him about that during the so-called campaign debates, as I would have done.

And then there’s healthcare. “Nobody knew healthcare could be so complicated,” Trump said in February, revealing that he knows less than your average drunk person in a bar about America’s overly complex and wasteful mess of a nonsystem for providing medical services.

Candidate Trump vowed he would repeal and replace the Affordable Care Act upon taking office. He insists the Republican replacement proposals are better, showing his cluelessness about immoral changes that would not just make health insurance unaffordable for tens of millions, but would cause needless suffering and premature death. He is also unaware or untroubled by how gutting Obamacare to make way for Trumpcare would grant him and his super-rich peers a trillion dollars of additional tax cuts.

Trump’s own words illuminate the undeveloped space between his ears. When political strategists and pundits try to distill a Trump doctrine from his word salad, I often find myself laughing at their folly.

Trump’s own words show he is utterly unprepared for the job of city council member, yet he possesses the nuclear launch codes. Ignorance is not bliss, but death and disaster waiting for the right mix of circumstances.