It can be a revolutionary concept that allowing free thought to develop is beneficial to all! Especially when you live in a backward, retrograde, traditionalist society, ruled by a despot. Nevertheless, stimulating the free thought of everyone in society transfers immediately into greater flow of ideas, which in turn helps the country's scientific development immensely.
This is the tree's uber-Policy! It both upgrades one of the central science buildings, the University (which now increases base Science output by a total of 50%), and adds Science production to the Trading Post tile improvement. Gold-oriented empires will get great immediate benefit from this Policy, since they usually build this type of improvement more. But any empire with lots of jungles will benefit as well: the Trading Post is the only improvement which can be built in a jungle without destroying it, and its native +2 Science yield is then upgraded by the improvement to a total of +3, which is then upgraded by the 50% bonus of the University!
Acquiring this Policy is a great strategy for accelerating tech progression for any empire, even one that doesn't intend to develop the whole tree. You just need one other Policy before that (Humanism), and you'll get a serious boost in raw Science production, as well as faster Great Scientist progression.
For players pursuing a science victory, getting this Policy should be a very high priority. They should develop another Policy before rushing this one, though, so the recommended progression is Secularism, then Humanism, then Free Thought.
Free thought is the belief that knowledge should be gained through the application of science and reason, rather than from tradition or religious dogma. Theories should be tested scientifically and logically. If something can't be proven, it's foolish to believe in it. Blind faith is the arch enemy of free thinkers everywhere. Free thinking is an important part of Buddhist tradition. In the "Kalama Sutta," the Buddha states, "Do not accept anything by mere tradition... Do not accept anything because it accords with your scriptures... But when you know for yourselves - then do you live accordingly."