The Fifth Law of Trust is that Trust is Transferrable. The best way to describe it is by asking: did your parents tell you, when you were young, to never get into a car with a complete stranger? Especially if they offer you something just to get into the car with them? So, let me ask you, have you followed that advice?
My guess is that your answer is a definite Yes!
But in reality, you do. You enter a car with a stranger. You do that every time you enter a ride-sharing Uber or Lyft car. What do you personally know about the driver? Nothing. You never met the driver. The driver fits the definition of a perfect stranger.
So, why did you enter that car? Because of the Fifth Law of Trust: Trust is transferrable. You trust the company (Uber or Lyft) enough that they have done their checks to qualify that driver (even with recent finding by Uber). But more than that, you trust the 953 people (none of whom you know) who gave that driver a high rating. You trust the 4.9/5 rating that driver has, so you enter the car. How come you trust people you don't know? A lot if there is a large number of them. When someone you don't know asks to be your "friend" on Facebook and there is no friend you have in common, would you accept that request? You will probably be apprehensive about it, look at their profile to see if it is appropriate. What if you have 3 friend in common? You would probably look at who those friends are before you decide. If those are friends that you trust, you will likely accept the friendship request even with only 3 friends in common. What if you have 257 friends in common? You will likely not even check who those friend are. You have enough in common to accept that request.
The Fifth Law of Trust: Trust is Transferrable. If person A trusts person B and person B trusts person C then person A is likely to trust person C, even though it would not be to the extent that person A trusts person B, or person B trusts person C. But it's better than nothing. You don't start at zero trust.
And in comes the dark side of the Fifth Law of Trust. What if the person you trust tells you that they don't trust the person you don't personally know? Wouldn't you immediately develop a negative attitude towards that third person? What do you really know about them? Nothing.
All you know is that someone you trust doesn't trust them. And that's enough for you. You tend to believe everything negative you hear. After all, it comes from someone you know and trust, and it's about someone you don't know and, well, don't trust.
In 2015, I ran for office. Most people had a good impression of me. More people trusted me than not. And I simply judge this by the fact that I won the election. But I heard very negative things said about me. None of them were true. It's not that I'm perfect, or ever was, but those things were not true. I still hear them. Why? Because trust (or distrust) is transferrable. If someone you trust tells you something negative about someone you don't know, you will distrust that other person.
And that's the dark side of the Fifth Law of Trust. Trust is not the only thing that gets passed along through trusted people. Distrust does too. And so are rumors. Be careful with what you tell people who trust you about people they don't know.