I strongly believe in liberalism as an optimistic ideology, with its ultimate tenet being the fundamental goodness of the human spirit and of people in general. Besides that idealism, it's simply good politics to be positive and not insult people.
Actually liberalism is pessimistic in nature. It assumes that power corrupts and therefore to help the common man the state should be given as little power as possible, with what power it does have being used to prevent the use and accumulation of power by narrow interests.
Wait a moment, you probably meant the new fangled version that believes that in order to help the common man, we need to concentrate power in bureaucrats and the like. It certainly is optimistic in assuming that those bureaucrats will be both knowledgable and motivated primarily by the common good.
About the only thing that unites the two liberalisms is the tenet that the good of the common man should be the primary concern of how to organize a government.