We can surely say that happiness either exist or does not exist. Philosophically treated, happiness either the life of wisdom (Stoics’ definition) or the ideal of imagination (Kant’s definition). Not choosing any side prematurely, we should at least go with Kant against the conventional image of happiness as the pile of things quenching all the physical need of the man.
Living through external, ever in the quest for wealth, honor, and sensual pleasure (Spinoza’s three types of affects), people are running into the abyss of non-being. To find a way out, we should reconsider our concept of knowledge and its practical aspects. Knowledge is not a dead thing that only applies onto externals. It is the most useful thing (if the word thing can be used here at all), which can lead us to the sanest life. And that life with the unity of thinking and action we could call the genuine happiness.