Meaning of 心さえ in 探索する心さえ忘れなければ


I encountered this sentence in the Cave Story (洞窟物語) game. It appears when I
pick up a device that gives me ability to look at a map.

> 探索する心さえ忘れなければ、いつか外に出られよう。私はそれを願う。

Unfortunately I can’t get the meaning of the first part. Let’s say that the 心
is some kind of willpower. “If I don’t forget my will to explore… at some
point I will be able to go out. That’s what I wish for.”

I don’t know. The whole 探索する心さえ忘れなければ construct looks extremely cryptic to me.




It seems you hit a snag with さえ. One of さえ's usages, as explained in Google's
definition, goes something like:

> 《「ば」など条件化の表現を伴って》 後ろに言う事が、その前に言う事だけの条件で満たされる意を表す。

This sense occurs with the [已然形・仮定形
(hypothetical)](https://ja.wikipedia.org/wiki/%E5%B7%B2%E7%84%B6%E5%BD%A2) of
a verb and expresses a condition. It works in roughly a similar way to "as
long as", and sometimes can also be rendered as "unless" in sentences.

For example, this line means:

> メールアドレスさえあれば、誰でも登録できます。  
>  Anyone can log into the account, as long as they have the email address.

