XL. I would recommend it to those who take delight in philosophy, to endeavour to inform themselves, whether it is not probable, that all other mixtures are impregnated with these particles; for if that should be found to be the case, we should discover the cause of the descent of heavy bodies; for there being in the earth the magnetic virtue, and in all other mixtures particles of iron, in spite of all our endeavours to separate them, they always would be brought together again by attraction. But as he who is a lover of the truth, should conceal no objection that may be made to any supposition that he advances, I will not dissemble, that I find a terrible one against this idea of mine; which is, that according to this system, iron should be heavier than gold; for although we should admit, that some iron, or magnetic particles are mixed with the gold, it is not credible, that the quantity of them should be equal to those in the iron itself; for if that was the case, the load-stone would attract the gold, as it does the iron. But whether there is in the terraqueous globe, another attractive quality distinct in kind from that of the load-stone, in virtue of which, all bodies may be disposed to approach it which we call heavy, by having in themselves a propensity to do it correspondent to that there is between the load-stone and the iron, is very difficult to be proved. ON SCEPTICAL PHILOSOPHY. SECT. I. I. There is so great a latitude in scepticism, and its gradations are so different, that according to the various extension that is given to the meaning of the word, it is used to describe the most extravagant error, and the most prudent mode of philosophizing. Rigid scepticism is a wild delirium, moderate is prudent caution. But those who in this age, have undertaken to combat the moderate sceptics, have either from ignorance or malice, confounded them with the rigid. When I reflect how gross a thing ignorance must be in such a case, it makes me think they acted from malice, and when I consider how detestable a thing malice is, it makes me conclude what they did was through ignorance. II. Although the Greek word _scepsis_, from whence sceptic and scepticism are derived, signifies inquisition, investigation, and speculation, custom has in a great measure altered the meaning of the term; on which account, sceptical at this day, implies doubt, or doubting; and scepticism, that particular avowal which sceptics make of doubting, or withholding their assent to all matters, that are liable to be controverted or disputed. III. This doubt or suspension of assent, may be more or less rational, in proportion to the greater or less extent that is given to it, or according to the matters to which it relates. Thus, although doubting of many things would be prudence, doubting of all would be madness. SECT. II.