The greater number of those who study nature, frequently do not consider, that prejudiced eyes will never discover more than that which they have previously determined to find: as soon as they perceive facts contrary to their own ideas, they quickly turn aside, and believe their visual organs have deceived them; if they return to the task, it is in hopes to find means by which they may reconcile the facts to the notions with which their own mind is previously tinctured. Thus we find enthusiastic philosophers, whose determined prepossession shews them what they denominate incontestible evidences of the systems with which they are pre-occupied, even in those things, that most openly contradict their hypothesis: hence those pretended demonstrations of the existence of theories, which are drawn from final causes--from the order of nature--from the kindness evinced to man, &c. Do these same enthusiasts perceive disorder, witness calamities? They induct new proofs of the wisdom, fresh evidence of the intelligence, additional testimony to the bounty of their system, whilst all these occurrences as visibly contradict these qualities, as the first seem to confirm or to establish them. These prejudiced observers are in an ecstacy at the sight of the periodical motions of the planets; at the order of the stars; at the various productions of the earth; at the astonishing harmony in the component parts of animals: in that moment, however, they forget the laws of motion; the powers of gravitation; the force of attraction and repulsion; they assign all these striking phenomena to unknown causes, of which they have no one substantive idea. In short, in the fervor of their imagination they place man in the centre of nature; they believe him to be the object, the end, of all that exists; that it is for his convenience every thing is made; that it is to rejoice his mind, to pleasure his senses, that the whole was created; whilst they do not perceive, that very frequently the entire of nature appears to be loosed against his weakness; that the elements themselves overwhelm him with calamity; that destiny obstinately persists in rendering him the most miserable of beings. The progress of sound philosophy will always be fatal to superstition, whose notions will be continually contradicted by nature. Astronomy has caused judiciary astrology to vanish; experimental philosophy, the study of natural history and chemistry, have rendered it impossible for jugglers, priests or sorcerers, any longer to perform miracles. Nature, profoundly studied, must necessarily cause the overthrow of those chimerical theories, which ignorance has substituted to her powers.