contemporary particle physics) that make many universes possible and therefore find it convenient to imagine all of them actual. With only one actual universe, and with no basis other than the limitations and predilections of the human mind to distinguish possible and impossible universes, we lack the conditions for a well-formed estimation of probabilities.
We come to recognize speculative groundlessness by facing the interminable and contestable character of the presuppositions on which all knowledge and belief rest. Every claim about the world relies on assumptions, and each layer of assumptions on further layers of assumptions. We cannot justifiably bring this layering of presuppositions to a halt by an appeal to self-evidence, for example, to the self-evident status of the axioms of Euclidean geometry. Our sense of self-evidence remains parasitic on our perceptual apparatus, which evolved in our embodied organisms to serve limited, practical goals.
Our more comprehensive claims about the world have an irreducible pragmatic residue. If we cannot bring the chain of our presuppositions to an end by an appeal to self-evidence, we can nevertheless justify the conditional forms of understanding with which we are left by invoking the predictions and initiatives that they inform, motivated by particular interests. The hard core of speculative groundlessness is the existence of intractable limits to our natural knowledge of the natural world. Science, equipped with technology, extends these limits, but it does not abolish them. With its help, we continue to view the world from the vantage point of our embodied minds.
The failure of the ontological argument for the existence of God in the history of Western philosophy and theology is a particular expression of a wider problem.1 Nothing in the character and content of what we have discovered about nature alters the brute facticity of the world: the world just happens to be one way rather than another. If there is only one universe at a time, its most important attribute is that it is—that it just happens to be—what it is rather than something else.
When we put aside the fictions of a metaphysical imagination determined to overstep the bounds of understanding, usually in the service of an effort to reassure us and to reconcile us to our lot, we encounter the dominant undertaking of modern science from Galileo and Newton to today: to discern the immutable laws governing nature, expected to be written in the language of mathematics. The unified understanding of these laws would then fix the outer limit to our comprehension of nature. There are, however, two grave limitations to this approach to the most general features of reality.
The first limitation is that its methods are suited to the exploration of parts of nature rather than of the universe as a whole. What one might call the Newtonian paradigm of scientific inquiry studies parts of reality, regions of the universe. In each of these regions, it distinguishes stipulated initial conditions marking out a configuration space within which phenomena change according to laws that can be expressed as mathematical equations. What is an initial condition at one moment may become an explained phenomenon at another. The scientist-observer stands outside the configuration space in the timeless position of God.
This approach fails when it is applied to the universe as a whole. Yet it is precisely knowledge about the universe as a whole (rather than about patches of space-time) that we require to defeat or to circumscribe speculative groundlessness. When the subject matter is cosmological rather than local, the distinction between initial conditions and explained phenomena within a configuration space cannot be maintained. The observer can no longer imagine himself as standing outside the boundaries of the configuration; there is nowhere outside the universe to stand. He cannot observe or prepare copies of the states of affairs that he investigates; there is only one universe, or at least one observable universe, at a time.
The second limitation of the dominant practice of natural science as a model of cosmological inquiry is that it assumes a historically provincial view of how nature works. It pictures the relatively settled and cooled-down universe. In this universe, the constituents of nature, as described by the standard model of particle physics, are unchanging and, for all practical purposes, eternal. States of affairs can be clearly distinguished from the laws governing them. We can think of the laws of nature as the indispensable warrants of all our causal explanations, and of causal connections as particular instances of the workings of these unchanging laws. The range of the adjacent possible is tightly drawn: the ways in which, and the extent to which, some things can turn into others.
What science has already discovered, however, suggests that nature did not, and does not, always appear in this form. It has another, fiery and unsettled variant, in which it presented itself in the very early history of the universe and may present itself again. In this variant, what we now think of as the elementary and eternal constituents of nature did not yet exist, or were not organized distinctly, as they now are, as a differentiated structure. The laws of nature may not have been distinguishable from the states of affairs that they governed. Indeed, causal connections or successions may not have assumed a law-like form at all. The susceptibility of the phenomena to transformation may have been much greater than it subsequently became in the relatively settled and cooled-down universe that the science founded by Galileo and Newton takes for granted.
When we cast aside feel-good metaphysics, with its disposition to claim more than we can pretend to know, recognize the incompleteness of that scientific tradition as a basis for thinking about the universe, and nevertheless attend to the revolutionary empirical discoveries of twentieth-century science, we reach a view reaffirming our speculative groundlessness rather than overcoming it. According to this view, everything changes sooner or later: the types of things that exist as well as the regularities connecting them. Change changes. Causal succession, rather than being simply a construction of the mind, is a primitive feature of nature. It sometimes exhibits law-like regularity (in the relatively settled, cooled-down variations of nature), and sometimes fails to exhibit it.
What there is then at the limit of our understanding is not a universe that could not be other than it is, or a framework of timeless laws. What there is is impermanence, which we also call time, and which Anaximander described some 2,500 years ago at the beginning of both Western science and Western philosophy: “All things originate from one another, and vanish into one another, according to necessity … under the dominion of time.” Nothing in this view explains away our speculative groundlessness. On the contrary, everything converges to make its meaning both more precise and more acute.
The world has a history, extending backward and forward in time, even beyond the present universe. No final system of laws could tell us what this history was, or will be, or must be; the regularities of the nature are the products of this history even more than they are its source.
When we come to understand this history much better than we now do, we shall still be confined to play a tiny part in it. It remains foreign to our concerns. Its message continues to be that nothing is for keeps, and that everything turns into everything else.
What about us? That is the question lying at the heart of the problem of existential groundlessness. A response to our existential groundlessness would make sense of our situation in the world in ways that provide guidance for the conduct of life and for the organization of society. We may first seek outside ourselves a basis for an orientation to existence in our general understanding of the world and of our place in it. If such an understanding yields no clues, we are driven back on ourselves: on our biographical and historical experience and on our self-understanding. The question then becomes whether the very lack of a grounding outside ourselves can be turned into an incitement and a justification for our self-grounding.
Only if all these attempts fail are we then left face to face with our existential groundlessness. In every instance, a response to the threat of existential groundlessness must take account of the most frightening aspect of our situation: that we will die. If such a response cannot show us how we are to achieve eternal life, it must suggest at least the beginnings of an approach to how we are to live, given our mortality, our manifest human nature or the human nature that we can bring about, our fundamental needs and desires, and the intractable limits to what
