Truth and Sense-Certainty
For Hegel, the immediate grasp of the object is superceded by our experience of it. By this, Hegel means that though we may hold the presentation within our consciousness, we have not yet begun to experience it for ourselves, and therefore reflect on the object. Hence, certainty gives place for truth for Hegel.
If we need an object in order to understand ourselves, then being-in-itself and being-for-itself are the same thing. The being of consciousness-in-itself is that of mediation, of movement. Mediation is the function of consciousness. Its own being is always searching for another in order to understand the world and itself. It searches for the object (which is an other) which it can use to understand itself. However, by understanding itself through the other, it also becomes other through abstraction. For example, if we look in a mirror, we do not see ourselves per se but rather an abstraction of ourselves through the means of the mirror. Our identity then, is based on abstraction and not a foundational essence.
The empty inner being, which is at the start of the process of mediation i.e. the consciousness without any objects of reference, is no longer an essence. By this, Hegel means it is no longer complete in itself, but has rather becomes a moment in the development of self-consciousness. Consciousness, as self-consciousness gains two objects: the first being the object of sense certainty, the second being itself which it comes to understand by placing itself in relation to the object. Both being and universality now are no longer immediate, isolated and independent. Rather, they have become apart of the movement of mediation and have hence become dynamic and dependant on other functions in the process of understanding.
A desire for certainty makes self-consciousness aware that the object has its own independence. This desire for certainty is conditioned by the object itself, as desire is always for the other, which it aims to overcome to become complete. Yet is unable to supercede it as we return to where we begun through this negation of a negation. In other words, we end up coming full circle back into oursleves. To achieve any level of satisfaction, it must use the object to return back into itself so it can start the whole process again ad infinitum. Therefore rendering the subject and substance as self-conscious by both being extensions of each other (and hence becoming absolute). So when Hegel says self-consciousness exists for self-consciousness, he is refering to the fact that when the Subject becomes self-conscious of itself, it repeats the process by coming to understand how being-for-itself was a necessary part for the development of self-consciousness and therby kickstaring the process again ad infinitum.
The independance and dependance of self-consciousness
Self-consciousness only exists only through being acknowledged. In other words, through self-understanding. Self-consciousness does this by acknowledging itself as both the origin and destination of itself. Once consciousness has reached its destination, the destination becomes self-conscious but also the origin as well. From the destination where self-consciousness is currently posited, it views the origin (where it was originally just consciousness) as self-consciousness, as well by being apart of the process which lead to the destination. This starts the process of introspection once again and we come full circle by examining how we became self-conscious.
The play of forces, which previously occurred in the perceived object, now occurs for consciousness (beginning) and self-consciousness (destination). They recognize themselves recognizing the other. Though self-consciousness comes out of itself, it is still in itself as well. It is no longer simply one recognizing and the other being recognized, both now exist in a state of recognizing and being recognized. They each seek to overcome each other (i.e. Cause the death of the other), by raising the ceartainty of their own existance.