Clarify an idiom in a political text

Please carefully read the text below:

On 24 November, 1993, a meeting of Leftist intellectuals occurred in London under the auspices of the Institute for Public Policy Research (IPPR), which is a Labour-leaning think-tank. A short document was circulated in advance of the said meeting to clarify its purpose.

Among other things, the document declared that the task of the IPPR was: "To do what the Right did in the seventies, namely to break through the prevailing parameters of debate and offer a new perspective on contemporary British politics." The explanatory document also said, "Our concern is not to engage in a philosophical debate about foundations of socialism."

If this meant that those foundations were not the appropriate thing to talk about at the 24 November meeting, then that might have been right; not every thing has to be discussed at every meeting. But if what was meant was that discussion of philosophical foundations is not what the Left now needs, then I disagree, and if that indeed is what was meant, then it is curious that the breakthrough by the Right should have been invoked as an achievement for the left to emulate, for if there is a lesson for the Left in the Right's breakthrough, it is that the Left must repossess itself of its traditional foundations on pain of continuing along its present, politically feeble, reactive course. If the Left turns its back on its foundations, it will be unable to make statements that are truly its own.

Since I've heard only one definition of the part identified in bold, I am at a dead end. As you know, and according to Oxford's dictionary, the verb "repossess" means: To take back property or goods from SB who has arranged to buy them and can not pay.

Here, the object of verb is a thing not a person, but in the text, first,itself comes before of and its traditional foundations. As a result, I thought that this phrase might be an idiom and so has a different meaning with the original verb.

Please explain the meaning of this phrase.

"Repossess" is being used reflexively in the same manner that "possess" often is, as in "possess itself" or "possess oneself." It means to retake possession of its own accord, to take possession by its own force of will rather than having possession simply return to them.

In this context, it's saying that the left needs to purposefully and with clear intent take back their traditional foundations. Saying it this way demonstrates that returning to traditional foundations is a positive action taken by the left, that their doing so is not merely sliding back into old ways, a return to business as usual, which is how any kind of return to old ways could otherwise be interpreted.