作出这一决定的理由暂时还不清楚。

The reasons for this decision were not immediately obvious.

《牛津词典》

应该直截了当给出决定的理由。

The reasons for the decision should be made explicit.

《牛津词典》

做出这项决定的理由我已在报告里说明了。

The reasons for my decision are set forth in my report.

youdao

Please observe too that it is not his reason that will determine human actions but his will alone, free of the moderating control of reason.

注意这不是他仅凭意志,决定人类行为的理由,而是理性对自由意志产生了潜移默化的影响

耶鲁公开课 - 古希腊历史简介课程节选

Is there any particular reason that you decided to be a superman?

你决定做超人有什么特别的理由吗？

我就是超人 - SpeakingMax英语口语达人