The cause of the French system and the consideration part of the English system appear in the same time similar in function and very different.
You can observe that both institutions seem to exclude the contracts not wanted by or dangerous for society. By controlling the cause the motives of the party can be examined. It can be controlled if they are incompatible with the values of the society.
The English system seems in the first view be purely objective, the judges are exclusively searching for something of value attributed to the other party for its promise, benefit for the promisor or detriment for promisee.
But looking at the case law the control seems not to be as objective as such. Judges often seem often decide more considering if the contract should be uphold or if this could result in undesirable consequences.