Karl Jaspers, answered from the texts and cited to the page.
Being cannot be grasped as a whole. Every time thought reaches for it, what it seizes is a determinate being — matter, energy, spirit, life — and in absolutizing that mode, it has already missed what it was after.1 The horizon recedes; we press forward; a new horizon appears. Being itself always withdraws in the very moment its appearances confront us.2
What we call the Encompassing is precisely this: not the horizon present at any given moment, but the source from which all horizons emerge, never itself becoming an object, never visible even as a horizon — that wherein everything else appears, and due to which things remain transparent rather than merely what they immediately seem.3 Now, modes of being are the distinct ways in which the Encompassing announces itself.
Kant already discerned two: the world as the Encompassing in which being itself appears, and consciousness-in-general as the Encompassing that we are and that conditions every object for us.4 But there is more to what we are than consciousness-in-general. We are also Dasein — the living being with beginning and end, laboring and suffering, anxious and hopeful in its environment.5
We are Bewusstsein überhaupt, consciousness as such, through which alone anything becomes an object at all, through which we break beyond our mere environment toward the idea of a world.6 And we are Geist, mind, animated by ideas that are not themselves objects but function as impulses, as systematic orientation, as infinite tasks.7 Yet these three modes do not yet exhaust what we are.
Existence, consciousness-as-such, and mind are the modes in which we become objects in the world — open to biological, psychological, sociological inquiry.8 And there the desolation sets in: correct thought yields to mere correctness; imaginative abundance founders on reality; the void of nothingness seems the only limit.9 Am I nothing but an interchangeable point of valid inference, a deceptively beautiful bloom of mind?
The answer lies in Existenz — not another mode alongside the others, but their ground and animation.10 Existenz is the Encompassing not in the sense of a vast horizon of horizons, but in the sense of a fundamental origin, the condition of selfhood without which all that vastness becomes a desert.11 It cannot be objectified; there is no science of it as there is of life or thought.12
It appears only indirectly, through the three modes as its medium, and communicates itself only obliquely — limited, unintelligible in direct form, yet unmistakably present when one Existenz encounters another in genuine communication.13 And beyond all the modes of the Encompassing that we are, there is Transcendence — Being itself as absolute Encompassing, showing itself to no investigative experience, not even indirectly, yet as certainly "is" as it remains unseen.14
The world points beyond itself, or there is no Transcendence; if the world is everything, it closes.15 Whether it closes is not a question science settles. It is the question that possible Existenz lives.
When I think of being as matter, energy, spirit, life, and so on — every conceivable category has been tried — in the end I always discover that I have absolutized a mode of determinate being, which appears within the totality of being, into being itself. No known being is being itself.Philosophy of Existence, pp. 15–18
The encompassing always merely announces itself in present objects and within the horizons — but it never becomes an object. Never appearing to us itself, it is that wherein everything else appears.Philosophy of Existence, pp. 15–18
Rather, it is the source from which all new horizons emerge, without itself ever being visible even as a horizon... It is also that due to which all things not merely are what they immediately seem to be, but remain transparent.Philosophy of Existence, pp. 15–18
The encompassing appeared in two modes. The encompassing in which being itself appears is called the world. The encompassing that I am and that we are is called consciousness in general.Philosophy of Existence, pp. 20–21
We are dasein, being-there. Like all living things we live in an environment... The Comprehensive in this being alive becomes an object of inquiry in its manifestations, in the products of life, in physical forms, in psychological functions.The Perennial Scope of Philosophy, pp. 10–11
We are consciousness as such in the division of subject and object. Only what enters into this consciousness is being for us... We break through our mere environment to the idea of the world to which all environments belong.The Perennial Scope of Philosophy, pp. 10–11
We are mind. The life of the mind is the life of ideas. Ideas... function as impulses in us, as an abstract of the total purpose inherent in the object, as systematic method of penetration, adaptation, and realization, and as such they lead us.The Perennial Scope of Philosophy, pp. 10–11
These three modes of the Comprehensive — being-there, consciousness as such, mind — are the modes in which we are objects in the world; i.e. as this Comprehensive is objectified into a thing that confronts us, we ourselves become adequate empirical objects of biological, psychological, sociological and historical inquiry.The Perennial Scope of Philosophy, pp. 10–11
With our three modes of encompassing we are not yet ourselves. They leave us without direction, without a solid ground... Are we nothing but the ruthless egotism of our living existence, nothing but interchangeable points of correct thought, nothing but a deceptively beautiful bloom of the mind?Philosophical Faith and Revelation, p. 95
Existenz is the Encompassing, not in the sense of the vastness of a horizon of all horizons, but rather in the sense of a fundamental origin, the condition of selfhood without which all the vastness of Being becomes a desert. Existenz, although never itself becoming an object or form, carries the meaning of every mode of the Encompassing.Reason and Existenz, pp. 61–63
The central point of philosophizing is first reached in the awareness of potential Existenz.Reason and Existenz, pp. 61–63
Existenz as such is not to be observed in any manifestation... Existenz cannot be objectified, so there can be no science of it, as of life, thought, or imagination.Philosophical Faith and Revelation, p. 95
In those three modes there is unequivocal communicability, but Existenz is only indirectly communicable in the three media. Its communication limited unintelligible form of existential.Philosophical Faith and Revelation, p. 95
Being itself is the Transcendence which shows itself to no investigative experience, not even indirectly. It is that which as the absolute Encompassing just as certainly 'is' as it remains unseen and unknown.Reason and Existenz, pp. 61–63
There is transcendence only if the world does not consist only of itself, is not built upon itself, but points beyond itself. If the world is everything, then there is no transcendence.The Perennial Scope of Philosophy, pp. 10–11