Denn hier ist es, wo uns der Genius der Analogie als Schutzengel zur Seite stehen möge, damit wir eine an vielen Beispielen erprobte Wahrheit nicht in einem einzigen zweifelhaften Fall verkennen, sondern auch da dem Gesetz gebührende Ehre erweisen, wo es sich uns in der Erscheinung entziehen möchte.
‘Erscheinung’ here is probably best understood as the ‘object of perceptual intuition’ as Immanuel Kant describes in the Opus Postumum*: "What is an object in appearance, however, in contrast to the same object but as a thing in itself?” - i.e. it is unrepresentable for human reason, which suggests that it is transcendent, i.e. knowable only by God. However, Kant confuses the object of sense as the thing in itself and as Erscheinung, the appearance of what never shows itself, the thing in itself, i.e. what shows itself in appearances themselves, namely as forms of intuition, that must be able to be examples, that is show themselves by themselves through proving through testing many examples, so that if one case is doubtful, i.e. that the tusks of an elephant are really the upper jaw as opposed to being part of the skull, which they appear to be, we apply the law (the universal) to the single doubtful case to see if it holds up. Thus something must have an 'explicit exhibition' (it must be available) in order to be perceived, and if it doesn't, we know from the universal law (that we have determined through many, well-tried examples) that it is probably true. Thus the Erscheinung (appearance) is properly speaking something that is hidden, or not immediately given, in what is seen at first.
*Kant, Opus postumum (trans. by Förster and Rosen, 1995) 22:43-44, p. 179
'mögen' in the first line (Denn hier ist es, wo uns der Genius der Analogie als Schutzengel zur Seite stehen möge) can also express a command, so I've translated it as 'shall' to emphasise the importance of analogy here. This usage is formal and rather old-fashioned [Durrell, Martin, and A. E Hammer, Hammer’s German Grammar and Usage (Chicago: McGraw-Hill, 2002), 16.2 (g) (iii), p. 327]
'Analogie' here means something like a relationship between two relationships, i.e. between the particular example (the doubtful case) and the set to which it belongs, the tried-and-tested universal 'law'.
Because this is where the genius of analogy shall stand by our side as a guardian angel, so that we will not fail to recognise one single, doubtful case in the proven-through-many-examples truth, but to bestow on the law its due honour, too, where the appearance (Erscheinung) may not show itself to us.
Many thanks for all the help, this translation is by no means perfect, but it's getting there.