Source: Prof Michael Sandel, Justice: ..., Episode 06: "MIND YOUR MOTIVE"
47:30 and here Kant distinguishes between persons on the one hand, and things on the other. 47:38: Rational beings are persons that don't just have a relative value for us, but if anything has they have an absolute value, an intrinsic value.
47:50 That is, rational beings have dignity that are worthy of reverence and respect.
47:56: This line of reasoning leads Kant to the second formulation of the Categorical Imperative which is this:
Act in such a way that you always treated humanity,
♦ whether in your own person or in the person of any other, ♦
never simply as a means, but always at the same time, as an end.
48:21: So that's the Formula of Humanity as an End.
Why did Kant (or the German to English translator) use in? I know that the 1st ed. of Critique of Pure Reason was published in German in 1781, but I still want to rationalise or understand this use (even if it's archaic), which would've never occurred to me.
I would've written the clause surrounded by ♦, as follows instead:
1. ♦ whether yourself or any other person , ♦
Footnote: I don't know which English translation Prof Sandel quoted, but please edit this if anyone does. If anyone wants to see the quote in print, see here for example.