Larry Brilliant:The case for optimism

TED 2007
Larry Brilliant:The case for optimism (script)
Summary
The year before the speaker told this speech, his TED talk told us that he and his team worked to eradicate smallpox. Although it came back sometimes finally it's eradicated at that time when there was no smallpox program. Smallpox killed more people than all the wars in history. Thus he said that it makes us optimistic. It's because it created a bond by working together and fighting against it beyond countries, every race, every religion and every color.
He lastly said how they can't make you feel optimistic for the future though I think that this is dangerous.
It's because it sounds like we don't have to do anything for solving our world problems but our world problem is only one.
The last sentences should be explained that we can fight alongside each other to solve our world problems from now also because we created the bond to eradicate smallpox difficulty found. His optimistic thoughts should make to use for fighting to our future problems.
Words in this story
legislation /  law(s), body of laws, rules, rulings
conquer / overcome.  defeat, beat, vanquish, trounce
reignite / ignite or cause to ignite again