Various versions of the Qur'an render this verse very differently:

Pickthall	Hilali & Khan	Shakir	R. Khalifa	M. Asad
They are asking thee concerning the Spirit. Say: The Spirit is by command of my Lord, and of knowledge ye have been vouchsafed but little.	And they ask you (O Muhammad) concerning the Ruh (the Spirit); Say: "The Ruh (the Spirit): it is one of the things, the knowledge of which is only with my Lord. And of knowledge, you (mankind) have been given only a little."	And they ask you about the soul. Say: The soul is one of the commands of my Lord, and you are not given aught of knowledge but a little.	They ask you about the revelation. Say, "The revelation comes from my Lord. The knowledge given to you is minute."	AND THEY will ask thee about [the nature of] divine inspiration. Say: This inspiration [comes] at my Sustainer's behest; and [you cannot understand its nature, O men, since] you have been granted very little of [real] knowledge.

The translators have apparently great difficulty in understanding what this verse is talking about. Maybe the author of the Qur'an had the same problem. Could it be that he did not understand the question asked, and being too embarrassed to request a clarification of the question, he decided to play it safe and responded that this is one of the issues that will remain God's secret?