The basic philosophical questions of economics blend with those of political philosophy and ethics. One such concern is whether we can compare and measure different levels of well-being in economic terms, given that the sources of value are diverse, and only partially concerned with economic activity. Other problems include the difficulties of achieving a social welfare function, of understanding the conception of the free economic agent who exercises choices in the market, and of deciding whether state interference in the market, whether by taxes or by indirect methods such as monetary levers, interfere with basic liberal rights. See also Austrian school, Hayek, Keynes, labour theory of value, Marx, money, Protestant work ethic, Say’s Law, Smith.