The most important idea of the nineteenth century in Britain was that everyone had the right to personal freedom, and this became the basis of capitalism. This idea, which had originated with Adam Smith in the eighteenth century, spread widely due to the popularity of his book The Wealth of Nations. After Adam Smith, several capitalist economists argued that the government should not interfere in trade and industry at all. Fewer laws, they claimed, meant more freedom, and freedom for individuals would lead to happiness for the greatest number of people. These ideas were eagerly accepted by the growing middle class. However, it soon became very clear that the freedom of factory owners to do as they pleased had led to slavery and misery for the poor, not to happiness or freedom. By 1820, more and more people had begun to accept the idea that the government must interfere to protect the poor and the weak. The result was a number of laws to improve working conditions. For instance, one of the laws, which went into effect in 1833, limited the number of hours that women and children were allowed to work.