A network of voluntary scientific societies and a popular literature on technology and political economy brought political economists, scientists and popular or journalistic commentators into contact with the provincial and industrial middle classes. A platform which brought these groups even closer was that of political debate. Where technology became a matter of economic policy, industrialist, worker and political economist debated with each other directly. A debate on commercial and economic policy would challenge a theorist both to apply and to develop his ideas. Equally, it would open an avenue for political action on the part of particular commercial and industrial interest groups. Above all, the policy debate highlighted the key role of ideas in social practice. For ideas acted to translate the crude opinions of particular interest groups into a generalisation of some theoretical conviction. Theory and systems of ideas played a definite part in the acceptability of argument, and in this way functioned as limits on the legitimacy of action. Moreover, the types of argument used in a policy debate reflected the position not only of their proponents but of those whom they sought to persuade. On the one hand, the group which stood to benefit from the acceptance of certain policies naturally phrased its arguments to advance these. But their arguments had equally to extend to the antagonistic group which had to be convinced. Politicians, therefore, often used the terms and concepts of their foes in order to gain their ear, and their arguments appealed to the general interest rather than to self-interest.