You require my opinion on a very difficult subject, upon which clouds and darkness rest. I do not pretend to have made up my mind on the nature, and degree of happiness reserved for the virtuous in a future system of existence. Every position has its difficulties; yet, may we not justly hope, — that as virtuous friendship affords the purest satisfaction in this world, it will also constitute a great part of our enjoyment in the next? This is a rational, a scriptural, and a soothing idea; and besides according the consolatory expectation of renewing those connections, the touching and tender ties of which have been dissolved by death, is a stimulus1 to mental improvement, by giving rise to the emulous wish, of preparing ourselves by cultivating our intellectual powers, for the society of the great and good minds, which we have been prevented from enjoying by local circumstances.
I am likewise sometimes inclined to think — that there will be a future state of recompense for the whole sensitive, as well as intelligent creation; otherwise, those unfortunate animals who are victims to the barbarity of human brutes, are created only for misery: a merciful Being must surely, in forming creatures capable of sensation, have intended their happiness, according to their different capacities of enjoyment; and raised a man above the rest, not to tyrannise, but as he is endowed with faculties superior to all the other orders of material creation, to rule with moderation, and guide all according to the purposes of heaven; so that each is made for each, for reciprocal benefit and kindness. But to return.
Respecting the exact nature of the happiness reserved for those, who after “continuing patient in well-doing will reap if they faint not,” — the Scriptures are silent, merely speaking of it, as what eye hath not seen, nor ear heard, neither hath it entered into the heart of man to conceive: lest, as Dr. Blair admirably observes,  we should be so absorbed in the contemplation of future felicity, as to be unfitted for properly fulfilling the duties by which we are to acquire virtue in our several stations in this life. The silence of revelation on this topic has given rise to innumerable conjectures, coloured by the different tempers, and imaginations of the speculators; not any of which give me entire satisfaction. Highly as I revere Dr. Priestley, and much as I am indebted to his writings for liberal, sober, and just conclusions on various subjects, I cannot perfectly accord with him on this: I love not to think, that the next would will not materially differ from this, or that we may be obliged to labour for our subsistence. An unquenchable thirst after perfection, an ever ardent and restless pursuit after something — “higher, more powerful, more living than visible nature” — surely point to a nobler destination! Neither am I at all inclined to adopt the torpid doctrine of a heaven of rest; still less the monotonous one of external hallelujahs, or psalmody; nor the mystic reveries of incessant, intense, extatic contemplation.  The notion of soaring from planet to planet, on celestial embassies, however flattering to the active emulation of our nature, also appears to me more Miltonic, than scriptural, or philosophical. On these topics we can only reason from analogy, taking Revelation for our guide; which while it promises the resurrection of the body, speaks of that body as changed and spiritualized. “Sown a natural, but raised a spiritual body.” By which I understand enlightened, refined, and purged from gross self-love.
In this world, intellectual pleasures afford the most elevated and real gratification, — the pursuit after truth, the benevolent affections —
“Knowledge, conscious peace, and virtue pure.”
may we not then suppose, that in a superior degree, and in constant progression and improvement, such will be the sources of our felicity in the next? I cannot conceive of greater happiness, than in the enjoyment of a society consisting only of the  wise and virtuous; where there will be no jarring interests, no sordid passions, no narrow prejudices, nothing little, mean, or vile: add to this immortality, and what remains to be desired? When history brings all ages to view, and we trace the progress of heroic virtue; when we hear of, and read the works by which great men have perpetuated their names; when we turn with horror and contempt from vice and folly, and sigh for an opportunity to inspect the sacred moments of elevated minds: when we regret the lapse of time, and the hours that pass away unenjoyed, and unimproved; when we feel the approach of age, benumbing our faculties, and blunting our sensibility; when we —
“Weep o’er friendships early bier,
And drop the tear on beauty’s tomb:” —
What an exhilarating, what a cheering prospect, is that of waking to flourish in immortal bloom! and joining the society of the just made perfect! It is this hope only which can inspire true fortitude, and sustain in the trying hour. Virtue is undoubtedly  in a great measure its own reward; as vice, being contrary to the frame of our nature, carries with it consequences necessarily destructive: yet we need a stimulus2 still more vivid and powerful; and this Christianity affords, in teaching a resurrection from the dead, and a future moral retribution. He who wishes to deprive us of this hope is an enemy to his species, and to society, and ought to be shunned and dreaded. — “Avoid those, who under the pretense of explaining natural causes, plant the most destructive doctrines in the hearts of men: who while they deprive the afflicted of the last consolation in their misery, take from the rich and powerful, the only check to the indulgence of their passions, and eradicate from the heart the remorse of guilt, and the hopes of virtue, absurdly calling themselves the friends, and the benefactors of mankind.”*
Every opinion that has a virtuous tendency, is entitled to our respect and support; such a tendency affords the test of  truth. If it were possible for a messenger from heaven to teach a doctrine malevolent in its principle, or pernicious in its practice, we ought to reject it with horror. Virtue and happiness can never be separated and are almost synonymous3; adventitious, and external circumstances are lighter than vanity, compared with the peace which results from a well-ordered mind. As real happiness then is only to be obtained by cultivating and improving the higher powers of our nature, and in proportion to our progress in wisdom and virtue, it will be vain to expect a glorious immortality from using particular phrases, or subscribing to certain opinions; unless purity of conduct, and spirituality of mind, fit us for those regions where nothing sensual, or worldly can enter. Let us not deceive ourselves, but remember the caution of our Saviour. “It is not he that sayeth Lord, but he who doeth the will of the Father which is in Heaven, that shall enter into the kingdom of glory.”
I am, &c.