Science Is Uncertain.

What I Am Going To Tell You About Is What We Teach Our Physics Students In The Third Or Fourth Year Of Graduate School... It Is My Task To Convince You Not To Turn Away Because You Don't Understand It. You See My Physics Students Don't Understand It... That Is Because I Don't Understand It. Nobody Does.

What Is The Fundamental Hypothesis Of Science, The Fundamental Philosophy? We Stated It In The First Chapter: The Sole Test Of The Validity Of Any Idea Is Experiment. ... If We Are Told That The Same Experiment Will Always Produce The Same Result, That Is All Very Well, But If When We Try It, It Does Not, Then It Does Not. We Just Have To Take What We See, And Then Formulate All The Rest Of Our Ideas In Terms Of Our Actual Experience.

'conservation' (the Conservation Law) Means This ... That There Is A Number, Which You Can Calculate, At One Moment-and As Nature Undergoes Its Multitude Of Changes, This Number Doesn't Change. That Is, If You Calculate Again, This Quantity, It'll Be The Same As It Was Before. An Example Is The Conservation Of Energy: There's A Quantity That You Can Calculate According To A Certain Rule, And It Comes Out The Same Answer After, No Matter What Happens, Happens.

I Think It's Much More Interesting To Live Not Knowing Than To Have Answers Which Might Be Wrong. I Have Approximate Answers, And Possible Beliefs, And Different Degrees Of Uncertainty About Different Things, But I Am Not Absolutely Sure Of Anything. There Are Many Things I Don't Know Anything About, Such As Whether It Means Anything To Ask "why Are We Here?" I Might Think About It A Little Bit, And If I Can't Figure It Out Then I Go On To Something Else. But I Don't Have To Know An Answer. I Don't Feel Frightened By Not Knowing Things, By Being Lost In The Mysterious Universe Without Having Any Purpose - Which Is The Way It Really Is, As Far As I Can Tell.

A Philosopher Once Said, 'it Is Necessary For The Very Existence Of Science That The Same Conditions Always Produce The Same Results.' Well, They Don't!