Доверяй, но проверяй (see below)

"How many legs does a dog have if you call the tail a leg? Four. Calling a tail a leg doesn't make it a leg."

Abraham Lincoln, 16th president of the United States.

Misinformation, disinformation, or fake news in today's parlance, is not new, it's been around as long as people have.

Does it really matter? It does really matter.

Acting on, re-posting, or just claiming something to be true you are not certain is true, suggests you are lazy.

Doing any of those things knowing the basis for your claim is not true, suggests you are a liar.

As President Ronald Reagan repeatedly said, "Trust but verify"

("Trust but verify" is an English translation of the Russian proverb Доверяй, но проверяй taught to Reagan by Suzanne Massie, American author of the book Land of the Firebird: The Beauty of Old Russia, and advisor to President Reagan regarding his negotiations with Mikhail Gorbachev, then President of the Soviet Union.)

TRUST BUT VERIFY, JUST NOT TOO MUCH

"A man who trusts nobody is apt to be the kind of man nobody trusts."

Harold Macmillan, 20th century Prime Minister of the United Kingdom.

I've never met anyone who trusted no one, but I have met those who trust too few.

You won't get very far in this world without the help of others, many of which you will simply have to trust to do what they say they will do.

SOME, JUST NOT TOO MUCH

"Trust not too much to appearances."

Virgil, 1st century BC Roman poet

Because appearances may only be what might be not what is.

Anything important to you should be more than just apparent.

NO DOUBT

"Deep doubts, deep wisdom; small doubts, little wisdom."

Chinese proverb

Assume that you are certain of, be little, that you must become certain of, great.

The reverse will only disappoint.

THE LIMITS OF PERSONAL CONFIDENCE

"It is a bad plan that admits of no modification."

Publilius Syrus (1st Century BC) Roman writer and poet.

Being sure of yourself is a good thing.

Just not as much as being willing to verify what you believe to be true, actually is.

Not all of it will be.

TRUST BUT VERIFY

"Denial ain't just a river in Egypt."

Mark Twain 19th century American writer/humorist

And accepting something as true without any consideration for whether or not it is, is a form of denial.

That can get you in trouble.

WHAT IF YOU'RE WRONG?

"Every man takes the limits of his own field of vision for the limits of the world."

Arthur Schopenhauer

19th century German philosopher

Not sure that everyone does this or that those who do always do.

But even occasionally is too often.

Start by assuming what you believe to be true may not be.

I FIND THIS HARD TO BELIEVE

"Incredulity is the wisdom of the fool."

Josh Billings

19th century American humorist and lecturer

But only if what you are incredulous about results in you acting, or not, when you should or should not have.

What You Think Or What You Know?

"What you don't see with your eyes don't witness with your mouth."

Jewish proverb

In business you must separate what you think is true from what you know is true. 

Those who find you doing too much of the latter will soon not trust you to do the former.