It may seem crazy to doubt that our concept of reality is true.
But I think, to find the meaning of life we must answer the question:
is there an independent reality or not?
Imagine a scenario that is straight from a science fiction movie. 
The world around you is actually nothing more than an elaborate fabrication…
of some unknown superior intelligence. 
A giant supercomputer provides you with all your senses
from what you see to what you smell, hear and touch. 
But in fact you have no senses. 
Your body does not exist. You are just a brain in a jar. 
It may sound bizarre, but this is a genuine scientific hypothesis called: 
The simulation theory. 
For all we know, every one of our perceived reality is simply fed to us
by some all-powerfull supercomputer. 
And the simulation is so perfect that we never even notice. 
But here’s the crack: It doesn’t actually matter. 
It’s as Descartes said: We think, therefore we are. 
The hamburger could be nothing more than a piece of computer code. 
But our desire to eat it, is still our own desire. 
We still feel hunger… 
Our minds still exist, even if we are in a simulation. 
So doubting the true nature of reality serves no purpose. 
It’s simpler to just accept that there are fundamental limits to what we can know. 
Take this table, for example. 
How do you know if a table still exists if you go out of the room… 
and can no longer see it? 
For all you know, the table could pack up and disappear out the window.
It could take a visit to the International Space Station. 
Perhaps even fly to the moon.
All this before returning to the exact same spot and instance before you reenter the room. 
This, of course is a pretty unlikely scenario. 
But one we can’t rule out. 
It is much simpler to assume that the table stays put when we are not there. 
It is our best fit model of reality. 
This is essentially what we do in science. 
We create best fit models of how we believe 
the universe actually works. 
The ancient Greeks were the first… 
to build such scientific models. 
They suggested that the earth was a large sphere, motionless…
And fixed at the center of the universe. 
But later pioneering scientist like Copernicus and Galileo… 
found a much simpler and completely revolutionary model to describe these same observations. 
They proposed that the earth itself was spinning and orbiting the sun at the same time… 
along with all the other planets. 
But neither can be said to actually be true. 
Because they, like all models, are just models in our heads: 
The best fit of reality we perceive. 
In fact, physicists are forever creating ever more sophisticated models… 
And the truth of those models is impossible to establish. 
A good example of this came in the 1960s. 
When physicists devised a theory of really tiny bits of matter, called quarks. 
These quarks were proposed to be the building blocks of the subatomic particle called: 
A proton. 
The theory our model suggested that… 
these quarks were held together by a force… 
that got stronger as you tried to separate them. 
As if the quarks were bound by tiny rubber bands. 
This model also implied that there is no way one can ever see a single isolated quark. 
At first, some people were skeptical.
If something by its very definition can never be seen,
can it be said to exist?
Does it make sense to say that quarks are real or not? 
In vast particle accelerators like this one at CERN in Switzerland…
Scientists are on the hunt for quarks and other subatomic particles. 
By smashing protons together at incredible speed…
We can study the behavior of the tiniest particles in nature.
Although we haven’t enabled to directly observe quarks, 
we have seen evidence of particle behavior predicted by the quark model. 
So, do quarks exist?
The answer is they exist only as a model that works. 
That is as far as we can go.
This is called the concept of model dependent reality.
And I believe that lead us directly to the meaning of life.
To my mind, science has taught us something pretty remarkable:
We humans are highly complex biological machines behaving in accordance
with the laws of nature. Our brains create and sustain our conscious mind
through and extraordinary network of interacting neurons.
That consciousness creates a three-dimensional model…
of the outside world:
A best fit model that we call reality.
This reality is much more than what we see around us in our everyday life.
A vast array of ground and space telescopes have extended our senses.
Allowing us to see deep into space…
And build a much bigger model than ever before. 
As we peer further and further into the cosmos…
our reality has grown bigger and bigger still…
where once we saw a chink in heaven’s flow… 
We now see distant stars like our sun.
Many with their own planets and moons.
Then we discovered distant galaxies, home to billions more stars.
We have peered back in time.
All the way to the birth of the universe itself.
All this, the entire 13.7 billion year history of the universe…
exists as a model inside our minds.
So, where does this leave us with finding a meaning to life?
The answer, I think, is pretty clear.
Meaning itself is simply another piece of the model of reality…
that we each built inside our own brains.
Take this mother and child. 
They each create their own little bubbles of reality in their conscious minds.
The youngster can create a detailed mental model
of his surroundings.
Even though he may not fully appreciate the fact he’s on the fifth floor.
The mother’s reality is also produced by her mind.
And for her, her love for her boy is as real as the telephone in her hand.
In short: the brain is responsible for not only the reality we perceive…
but for our emotions and meaning too.
Love and honor, right and wrong…
are part of the universe we create in our minds…
just as a table, a planet or a galaxy.
It’s pretty remarkable to think that our brains…
which are essentially a collection of particles working to the law of physics… 
have this wonderful ability to not only perceive realty…
but to give it meaning, too.
The meaning of life is what you choose it to be. 
Personally, I like to think that it is everyone of us that gives meaning to the universe.
We are, as cosmologist Carl Sagan once said:
The universe contemplating itself.
Meaning can only ever exist within the confines of the human mind.
And in this way, the meaning of life is not somewhere out there…
but right between our ears.
In many ways, this makes us The Lords of Creation.
