Best Gains must have the Losses' test –

Best Gains  must have the Losses' test –
To constitute them – Gains.
                                                                     F499 (1863)  J684

Not "Revelation" – 'tis – that waits,
But our unfurnished eyes.
                                                                      F500 (1863)  J685

Both of these aphorisms came from a letter (L280) to Thomas Wentworth Higginson. Dickinson had anticipated a visit from him the previous summer, but learned later in the year that he had gone away to war. Up until that time he been a captain in a Massachusetts Infrantry division, but following an injury he was appointed colonel of the First South Carolina Volunteers – which was the first regiment of freedmen (the Secretary of War required that the regiment be led by a white officer; Higginson was a good choice, then, for he was an ardent abolitionist and human rights activist).
       In her letter Dickinson says that she had discovered what happened "by accident, as I find Systems are, or Seasons of the year, and obtain no cause – but suppose it is a treason of Progress – that dissolves as it goes." Her affectation of bemusement is odd as, according to biographer Thomas Johnson, The Springfield Republican published detailed information about Higginson and his troops. Also odd is the seemingly dismissive tone towards the war, now at its bloodiest. Earlier in the letter she is even more dismissive: "War feels to me an oblique place – Should there be other Summers, would you perhaps come?"
       But perhaps Dickinson's goal is to inject a bit of wit and cheer, for she ends the letter this way:

Should you, before this reaches you, experience immortality, who will inform me of the Exchange? Could you, with honor, avoid Death, I entreat you – Sir – It would bereave
                Your Gnome

As for the aphorisms (I resist calling them poems), they both have a theme of discovery. The value of a supposed gain is established by the "test" of believing it lost. By this means, Dickinson discovered that a visit from Higginson would be a great gain.
       The second aphorism is introduced by the comment, "I was thinking, today – as I noticed, that the 'Supernatural," was only the Natural, disclosed –".  This is very much Enlightenment thinking. It isn't that "Revelation" is needed to reveal the veiled truth, but that our eyes are not sufficiently developed. Or, as Dickinson wrote in "'Faith' is a fine invention" (F202)
Faith" is a fine invention

For Gentlemen who see!
But Microscopes are prudent
In an Emergency!

When faced with a mystery, don't wait in faith that a revelation will occur; get a microscope or better glasses!

What I like from this letter to Higginson is that Dickinson says she told the "Best Gains" lines to her big Newfoundland dog, Carlo, and that "My Shaggy Ally assented." I love to think of the small Dickinson confiding in the giant shaggy dog.