Hegel’s account of being-for-itself follows that of “being-there” in the Doctrine of Being. Being-there emerges from becoming and is the moment of determinancy or quality accomplished through negation of what is other. Being-there thus defines itself in terms of limit. The difficulty is that limit is shared by both what is limited and its other. Consequently, the being-there that strives to limit itself finds itself passing into its other. Being-for-itself is the response, the attempted “cure”, to this endless passing over, and takes place through an attempted exclusion of the Other.

As Hegel puts it in The Encyclopedia Logic,

As relation to itself, being-for-itself is immediacy, and as relation of the negative to itself it is what-is-for-itself, the One— that which lacks inward distinction, thereby excluding the Other from itself. (paragraph 96)

Being-for-itself would like to maintain itself in its immediacy through the renunciation of the Other. As such it strives to constitute itself as One and only One, enclosing itself within itself and maintaining itself only as what-is-for-itself. It thereby seeks to abolish the Other and close it off, making the limit its own. In this regard, the One is indifferent to the others.

Hegel goes on to render what is implicit in this moment explicit, unfolding the content of the One.

The relation of the negative to itself is negative relation, and therefore distinguishing of the One from itself, the repulsion of the One, i.e., the positing of many Ones. In keeping with the immediacy of what-is-for-itself, these many [simply] are, and as a result the repulsion of the ones that [simply] are becomes their repulsion against each other as given, or their reciprocal exclusion. (Paragraph 97)

Wishing to hold fast to itself and constitute itself as One– for instance, as in the case of a body of theoretical propositions that would like to hold fast to themselves so as to maintain their identity immune from criticisms and other productive lines of inquiry –being-for-itself must necessarily distinguish itself from what it is not and actively exclude those other Ones. Paradoxically, in its attempt to maintain the integrity of its newfound identity or Oneness it thereby imbricates itself with what is Other. As such,

…the many are each one what the other is, each of them is one or also one of the many; they are therefore one and the same. Or, when the repulsion is considered in itself then, as the negative behaviour of the many ones against each other, it is just as essentially their relation to each other; and since those to which the One relates itself in its repelling are ones, in relating to them it relates itself to itself. Thus, repulsion is just as essentially attraction; and the excluding One of being-for-itself sublates itself. Qualitative determinancy, which in the One has reached its determinateness-in-and-for-itself, has thus passed over into determinancy as sublated, i.e., into being as quantity. (paragraph 98)

A negative relation is nonetheless a relation, and the One now discovers that its determinancy arises in and through its relation to the Other. Its relation to the Other has thus now been sublated as, where initially, the One saw the Other as the undoing of its own being-for-itself, it now sees its relation to the Other as constitutive of its own immediacy… Or rather, it now understands this immediacy to be necessarily mediated by this relation to the Other. It is in this respect that repulsion passes over into attraction as the One requires the Other to be what it is for-itself.