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Of the reason
from the resemblance of the external actions of ani- SECT.
XVI. mals to those we ourselves perform, that we judge their internal likewise to resemble ours; and the same principle of reasoning, carried one step farther, will make
animals. us conclude, that, since our internal actions resemble each other, the causes, from which they are derived, must also be resembling. When any hypothesis, therefore, is advanced to explain a mental operation, which is common to men and beasts, we must apply the same hypothesis to both; and as every true hypothesis will abide this trial, so I may venture to affirm, that no false one will ever be able to endure it. The common defect of those systems, which philosophers have employed to account for the actions of the mind, is, that they suppose such a subtility and refinement of thought, as not only exceeds the capacity of mere animals, but even of children and the common people in our own species; who are, notwithstanding, susceptible of the same emotions and affections as persons of the most accomplished genius and understanding. Such a subtility is a clear proof of the falsehood, as the contrary simplicity of the truth, of any system.
Let us, therefore, put our present system, concerns ing the nature of the understanding, to this decisive trial, and see whether it will equally account for the reasonings of beasts as for those of the human species..
Here we must make a distinction betwixt those actions of animals, which are of a vulgar nature, and seem to be on a level with their common capacities, and those more extraordinary instances of sagacity, which they sometimes discover for their own preservation, and the propagation of their species. A dog that avoids fire and precipices, that shuns strangers, and caresses his master, afiords us an instance of the first
PART kind. A bird, that chuses with such care and nicety III.
the place and materials of her nest, and sits upon her Of eggs for a due time, and in a suitable season, with all knowledge
and the precaution that a chemist is capable of in the most probability. delicate projection, furnishes us with a lively instance of
· As to the former actions, I assert they proceed from a reasoning, that is not in itself different, nor founded on different principles, from that which appears in human nature. 'Tis necessary, in the first place, that there be some impression immediately present to their memory or senses, in order to be the foundation of their judgment. From the tone of voice the dog infers his master's anger, and foresees his own punishment. From a certain sensation affecting his smell, he judges his game not to be far distant from him.
Secondly, the inference he draws from the present impression is built on experience, and on his observation of the conjunction of objects in past instances. As you vary this experience, he varies his reasoning. Make a beating follow upon one sign or motion for some time, and afterwards upon another; and he will successively draw different conclusions, according to his most recent experience.
Now, let any philosopher make a trial, and endeavour to explain that act of the mind which we call belief, and give an account of the principles from which it is derived, independent of the influence of custom on the imagination, and let his hypothesis be equally applicable to beasts as to the human species; and, after he has done this, I promise to embrace his opinion. But, at the same time I demand as an equitable condition, that if my system be the only one, which can answer to all these terms, it may
Of the reason
be received as entirely satisfactory and convincing. And that 'tis the only one, is evident almost without any reasoning. Beasts certainly never perceive any real connexion among objects. 'Tis therefore by experience they infer one from another. They can never by any arguments form a general conclusion, that those objects of which they have had no experience, resemble those of which they have. 'Tis therefore by means of custom alone that experience operates upon them. All this was sufficiently evident with respect to man. But with respect to beasts there cannot be the least suspicion of mistake; which must be owned to be a strong confirmation, or rather an invincible proof of my system.
Nothing shows more the force of habit in reconciling us to any phenomenon, than this, that men are not astonished at the operations of their own reason, at the same time that they admire the instinct of animals, and find a difficulty in explaining it, merely because it cannot be reduced to the very same principles. To consider the matter aright, reason is nothing but a wonderful and unintelligible instinct in our souls, which carries us along a certain train of ideas, and endows them with particular qualities, according to their particular situations and relations. This instinct, 'tis true, arises from past observation and experience; but can any one give the ultimate reason, why past experience and observation produces such an effect, any more than why nature alone should produce it? Nature may certainly produce whatever can arise from habit: nay, habit is nothing but one of the principles of nature, and derives all its force from that origin.
OF THE SCEPTICAL AND OTHER SYSTEMS OF
OF SCEPTICISM WITH REGARD TO REASON.
PART In all demonstrative sciences the rules are certain and
infallible ; but when we apply them, our fallible and sceptical and uncertain faculties are very apt to depart from them,
and fall into error. We must therefore in every reasyotems of philosophy. soning form a new judgment, as a check or control
on our first judgment or belief; and must enlarge our view to comprehend a kind of history of all the instances, wherein our understanding has deceived us, compared with those wherein its testimony was just and true. Our reason must be considered as a kind of cause, of which truth is the natural effect; but such a one as, by the irruption of other causes, and by the inconstancy of our mental powers, may frequently be prevented. By this means all knowledge degenerates into probability; and this probability is greater or less, according to our experience of the veracity or deceitfulness of our understanding, and according to the simplicity or intricacy of the question.
There is no algebraist nor mathematician so expert SECT. in his science, as to place entire confidence in any truth immediately upon his discovery of it, or regard
scepticism it as any thing but a mere probability. Every time he
regard to runs over his proofs, his confidence increases; but still more by the approbation of his friends; and is raised to its utmost perfection by the universal assent and applauses of the learned world. Now, 'tis evident that this gradual increase of assurance is nothing but the addition of new probabilities, and is derived from the constant union of causes and effects, according to past experience and observation.
In accounts of any length or importance, merchants seldom trust to the infallible certainty of numbers for their security ; but by the artificial structure of the accounts, produce a probability beyond what is derived from the skill and experience of the accountant. For that is plainly of itself some degree of probability; though uncertain and variable, according to the degrees of his experience and length of the account. Now as none will maintain, that our assurance in a long numeration exceeds probability, I may safely affirm, that there scarce is any proposition concerning numbers, of which we can have a fuller security. For 'tis easily possible, by gradually diminishing the numbers, to reduce the longest series of addition to the most simple question which can be formed, to an addition of two single numbers; and upon this supposition we shall find it impracticable to show the precise limits of knowledge and of probability, or discover that particular number at which the one ends and the other begins. But knowledge and probability are of such contrary and disagreeing natures, that they cannot well run insensibly into each other, and that because