As the human race, however, could not be improved in this way, without condemning all the bad specimens to celibacy, it is not probable that an attention to breed should ever become general; indeed, I know of no well-directed attempts of this kind, except in the ancient family of the Bickerstaffs, who are said to have been very successful in whitening the skins and increasing the height of their race by prudent marriages, particularly by that very judicious cross with Maud, the milk-maid, by which some capital defects in the constitutions of the family were corrected.
It will not be necessary, I think, in order more completely to shew the improbability of any approach in man towards immortality on earth, to urge the very great additional weight that an increase in the duration of life would give to the argument of population.
Many, I doubt not, will think that the attempting gravely to controvert so absurd a paradox as the immortality of man on earth, or indeed, even the perfectibility of man and society, is a waste of time and words, and that such unfounded conjectures are best answered by neglect.

I profess, however, to be of a different opinion.

When paradoxes of this kind are advanced by ingenious and able men, neglect has no tendency to convince them of their mistakes.

Priding themselves on what they conceive to be a mark of the reach and size of their own understandings, of the extent and comprehensiveness of their views, they will look upon this neglect merely as an indication of poverty, and narrowness, in the mental exertions of their contemporaries, and only think that the world is not yet prepared to receive their sublime truths.
On the contrary, a candid investigation of these subjects, accompanied with a perfect readiness to adopt any theory warranted by sound philosophy, may have a tendency to convince them that in forming improbable and unfounded hypotheses, so far from enlarging the bounds of human science, they are contracting it, so far from promoting the improvement of the human mind, they are obstructing it; they are throwing us back again almost into the infancy of knowledge and weakening the foundations of that mode of philosophising, under the auspices of which science has of late made such rapid advances.

The present rage for wide and unrestrained speculation seems to be a kind of mental intoxication, arising, perhaps, from the great and unexpected discoveries which have been made of late years, in various branches of science.