Therefore it is proper to put the belief in these implanted truths as a distinct power of the mind, and to call it "the reason." And as the belief of these truths is _common_ to all men, it is also proper to call it _common sense_.
CHAPTER XIII. NATURE OF MIND.--REGULATION OF THE THOUGHTS.
A system of natural religion includes not only the existence and natural attributes of the Creator, but his moral character and the duties owed to Him, to our fellow-beings and to ourselves.
To discover these by the principles of common sense, unaided by revelation, we must again turn to our own minds as our only directory. This demands a more enlarged consideration of many of the specific powers and operations of mind, as developed by experience and observation.
The mode by which the succession of our thoughts is regulated is intimately connected with several subjects to be discussed, and will, therefore, first receive attention.
It will be found that our _sensations_ and _perceptions_ vary in vividness and distinctness according to the strength and permanency of certain feelings of _desire_ which coexist with them. For example, we are continually hearing a multitude of sounds, but in respect to many of them, as we feel no desire to know the cause or nature of them, these sensations are so feeble and indistinct as scarcely ever to be recalled to the mind or recognized by any act of memory; but should we hear some strange wailing sound, immediately the desire would arise to ascertain its nature and cause. It would immediately become an object of distinct and vivid perception, and continue so as long as the desire lasted.
While one sensation becomes thus clear and prominent, it will be found that other sensations which were coexisting with it will become feebler and seem to die away. The same impressions may still be made upon the eye as before, the same sounds that had previously been regarded may still strike upon the ear, but while the desire to learn the cause of that strange wailing sound continues, the other sensations will all be faint and indistinct. When this desire is gratified, then other sensations resume their former distinctness and prominency.
Our _conceptions_, in like manner, are affected by the coexistence of emotion or desire. If, for example, we are employing ourselves in study or mental speculations, the vividness of our conceptions will vary in exact proportion to the interest we feel in securing the object about which our conceptions are employed. If we feel but little interest in the subject of our speculations, every conception connected with them will be undefined and indistinct; but if the desire of approbation, or the admonitions of conscience, or the hope of securing some future good stimulate desire, immediately our conceptions grow more vivid and clear, and the object at which we aim is more readily and speedily secured.