is the actor involved in any political causes?
Yes, in 2004, he encouraged students to vote in the 2004 U.S. presidential election.
Brad Pitt
Pitt visited the University of Missouri campus in October 2004 to encourage students to vote in the 2004 U.S. presidential election, in which he supported John Kerry. 
which was the debut film of brad pitt? "Thelma & Louise" which charitable causes does he support? One Campaign what is it about? It is an organization aimed at combating AIDS and poverty in the developing world.
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Brad Pitt [SEP] Humanitarian and political causes
Pitt visited the University of Missouri campus in October 2004 to encourage students to vote in the 2004 U.S. presidential election, in which he supported John Kerry. Later in October, he publicly supported the principle of public funding for embryonic stem-cell research. "We have to make sure that we open up these avenues so that our best and our brightest can go find these cures that they believe they will find", he said. In support of this he endorsed Proposition 71, a California ballot initiative intended to provide state government funding for stem-cell research. Pitt supports One Campaign, an organization aimed at combating AIDS and poverty in the developing world.