In enumerated lists, how to show the 1st word within square brackets?

Question

Consider the following code:

\begin{enumerate} %here external and internal should be within square brackets
  \item [external:] to make the outer realm (\textit{zahir}) shine
with the rules of the sharia, and
  \item [internal:] to free the inner realm
(\textit{batin}) from captivation by whatever is other than the Haqq.
\end{enumerate}

The words external and internal should be within square brackets but if I do it LATEX does problem---the left margin shifts. The output I want is:

1. [external:] ????????????????
2. [internal:] ???????????????