“Although the acquisition of fresh knowledge is the necessary precursor of every step in social progress, such acquisition must itself be preceded by a love of inquiry, and therefore by a spirit of doubt, because without doubt there will be no inquiry, and without inquiry there will be no knowledge, for knowledge is not an inert and passive principle which comes to us whether we will or no; but it must be sought before it can be won; it is the product of great labour, and, therefore, of great sacrifice. And it is absurd to suppose that men will incur the labour and make the sacrifice for subjects respecting which they are already perfectly content. They who do not feel the darkness, will never look for the light. If on any point we have attained to certainty, we make no further inquiry on that point, because inquiry would be useless or perhaps dangerous. The doubt must intervene before the investigation can begin. Here, then, we have the act of doubting as the originator, or at all events the necessary antecedent of all progress. Here we have that scepticism, the very name of which is an abomination to the ignorant, because it disturbs their lazy and complacent minds; because it troubles their cherished superstitions; because it imposes on them the fatigue of inquiry; and because it rouses even sluggish understandings to ask if things are as they are commonly supposed, and if all is really true which they from their childhood have been taught to believe. The more we examine this great principle of scepticism, the more distinctly shall we see the immense part it has played in the progress of European civilisation. To state in general terms, what in this introduction will be fully proved, it may be said that to scepticism we owe that spirit of inquiry which, during the last two centuries, has gradually encroached on every possible subject, has reformed every department of practical and speculative knowledge; has weakened the authority of the privileged classes, and thus placed liberty on a surer foundation; has chastised the despotism of princes; has restrained the arrogance of the nobles, and has even diminished the prejudices of the clergy. In a word, it is this which has remedied the three fundamental errors of the olden time, errors which made the people in politics too confiding, in science too credulous, in religion too intolerant. We have thus seen the rise of that scepticism which in physics must always be the beginning of science, and in religion must always be the beginning of toleration. There is, indeed, no doubt that in both cases individual thinkers may by a great effort of original genius, emancipate themselves from the operation of this law. But in the progress of nations no such emancipation is possible. As long as men refer the