Why do we use 〜ないで instead of 〜なくて before auxiliary ください?


I was taught in college that the 〜ない verb conjugation behaves like an
i-adjective, thus it has 〜く form, it takes 〜ければ for "if" scenario, it modifies
the noun that follows it etc. Also, I know that the 〜くて form of i-adjective
has overlapping roles with 〜て form of verb, such that it can be used to
combine the i-adjective or verb with the next predicate, e.g. 滑りやすくて転んだ and
転んで泣いた. However, while 〜て form of verb can be used before auxiliary ください, for
verbs that have been conjugated with 〜ない, instead of using the 〜なくて form with
ください, we have to use 〜ないで form instead.

I just learned from [sawa's answer for my previous
question](https://japanese.stackexchange.com/questions/3212/an-i-adjective-
immediately-before/3213#3213) that i-adjective (even with 〜くて form) cannot be
followed immediately by ください for the reason that the main verb is missing, but
〜なくて conjugation is attached to a verb so the issue of missing main verb
should not be there anymore. Yet, why is it still not 〜なくてください, but is
〜ないでください instead? Where's the missing link in my reasoning? And finally, how
does the 〜ないで form match with ください?




There is some Deep Magic going on here. Let me try to offer a theory which,
hopefully, will not muddy the waters further.

The ～て form of verbs (both positive and negative) implies a decision point.
That is, at some point in time, you choose to do something or not to do
something. Once this choice is made, it is irreversible.

Consider 食べてください. In effect, this request means, "At some point in the future,
please choose to go from your current state of _have-not-eaten_ to _have-
eaten_." Once you enter the state of _have-eaten_ , you cannot go back. You
cannot undo the action of eating.

With ～なくて, a second action always exists, even if it is implied. That is, the
decision is between not doing one thing and doing something else. 注意しなくて転んだ
means that at a certain point, you chose not to enter the state of paying
attention, and as a result you tripped. As with 食べてください, the decision (the
choice of states) is treated as a single point in time and is irreversible.

This is why ～なくて cannot take ください. With 食べなくてください, you are essentially saying,
"At some point in the future, please choose to go from your current state of
_have-not-eaten_ to _have-not-eaten_." This is illogical; you cannot change
from state A to state B when A and B are the same. What you really want to say
is, "Please stay in the state of _have-not-eaten_." But because ～て is limited
to a single decision point, it cannot handle the range of points expressed in
"stay in this state." To use an analogy from geometry, it is like the
difference between a point (a discrete, finite quantity of one) and a line (an
infinite quantity of points).

Because the action of staying in the state of _have-not-eaten_ (the action of
not entering the state of _have-eaten_ ) takes place over a range of time, the
～ないで form is needed. To explain why, consider what happens when we replace
ください with いる. We find the same problem with ～なくて:

> ○ 食べている eating (or remaining in the state of _have-eaten_ )
>
> × 食べなくている (grammatically incorrect)
>
> ○ 食べないでいる not eating (or remaining in the state of _have-not-eaten_ )

いる in these forms implies the continuation of a state. 食べている works because a
state-change was made at some point (食べて) and you are continuing in that state
(いる). 食べないでいる works because you started out in a state (食べないで) and are
continuing in that state (いる). But 食べなくている does not work because there is no
state-change in 食べなくて, therefore you cannot continue in it with いる.

