Neil deGrasse Tyson Intelligent Quotations

Perhaps we've never been visited by aliens because they have looked upon Earth and decided there's no sign of intelligent life.

I think that intelligence is such a narrow branch of the tree of life - this branch of primates we call humans. No other animal, by our definition, can be considered intelligent. So intelligence can't be all that important for survival, because there are so many animals that don't have what we call intelligence, and they're surviving just fine.

Intelligent design is a philosophy of ignorance.

I wonder if, in fact, we have been observed by aliens and upon close examination of human conduct and human behavior they have concluded that there is no sign of intelligent life on Earth.

Lots of people think, well, we're humans; we're the most intelligent and accomplished species; we're in charge. Bacteria may have a different outlook: more bacteria live and work in one linear centimeter of your lower colon than all the humans who have ever lived. That's what's going on in your digestive tract right now. Are we in charge, or are we simply hosts for bacteria? It all depends on your outlook.

I lose sleep at night wondering whether we are intelligent enough to figure out the universe. I don't know.

For all we know, the aliens have already done this and unwittingly concluded that there was no intelligent life on Earth. They would now be looking elsewhere. A more humbling possibility would be if aliens had become aware of the technologically proficient species that now inhabits Earth, yet they had drawn the same conclusion.

My only hope is that every other alien civilization isn't doing exactly what we are doing because then everybody would be listening, nobody would be receiving, and we would collectively conclude that there is no other intelligent life in the universe.

We are only intelligent by our own measures

Intelligent life can't be all that common because it's really rare on Earth and especially since we define ourselves to be intelligent. But in the eyes of an alien coming here who has the technology to make it here, they might observe us and conclude that there's no sign of intelligent life on Earth.