Why don't the upward forces equal each other in a simple pulley?

[AlbertE97]

As seen in the image below, a hand is pulling one end of a rope that is on a simple pulley, and the object W is pulling another end.

What I don't understand is what kind of force acts both objects P and W upward. The downward force is the force of gravity. Since I've learned that these kind of pulleys simply change the direction of the force, why shouldn't both the forces acting upward be equal to the mass of the other object times g?
(English my 2nd language)

 

[SteamKing]

Is P acting upward?

This seems like the time to perform a simple physical experiment.

 

[AlbertE97]

Nevermind, I've just learned it is the Tension force.