He earned his Ph.D. in applied math and theoretical physics from Cambridge University in 1964. While a post-doc at Cambridge, in 1972 he co-authored with Stephen Hawking the landmark book on cosmology and general relativity The Large Scale Structure of Space-Time.

Ellis has written extensively on science and religion and was awarded the Templeton Prize in 2004.

His deep knowledge of physics has influenced major Christian theologians who integrate the indeterminism of quantum physics into their concept of a divine being. Traditional theologians have argued that randomness in the universe is in direct conflict with a God who is omnipotent and omniscient.

As has been argued since Anselm in the eleventh century, God cannot be both omnipotent and omniscient. Moreover, random events invalidate the idea of God's foreknowledge.

The Christian concept of a benevolent and providential God is in further conflict with both classical deterministic physics and indeterministic quantum physics.

Ellis was a major contributor to a multi-year collaborative research program on the role of randomness in nature sponsored in part by the Vatican Observatory and the John Templeton Foundation.

In an important article in Nature, Ellis argued that complexity of hierarchical systems can explain the intentionality of human purpose, goal-directed action. He wrote

It is possible that what actually happened was the contextual emergence of complexity: the existence of human beings and their creations was not uniquely implied by the initial data in the early Universe; rather the underlying physics together with that initial data created a context that made the existence of human beings possible. Conditions at the time of the decoupling of matter and radiation 14 billion years ago were such as to lead to the eventual development of minds that are autonomously effective...

With this view, the higher levels in the hierarchy of complexity have autonomous causal powers that are functionally independent of lower-level processes. Top-down causation takes place as well as bottom-up action, with higher-level contexts determining the outcome of lower-level functioning, and even modifying the nature of lower-level constituents.

Stored information plays a key role, resulting in non-linear dynamics that are non-local in space and time...Consequently physics per se cannot causally determine the outcome of human creativity; rather it creates the ‘possibility space’ to allow human intelligence to function autonomously...

So far, attempts to relate physics to complexity... take us only a small step on this road.

Physics, Complexity.Causality. Nature, v.435, p.743, 2005

Complexity and chaos theory have been popular for the last few decades as an alternative to the ontological indeterminism of quantum physics. Hierarchical systems theory supports the emergence of new properties, even "laws." Ellis is correct that information plays a key role.

Information philosophy explains the reality of emergence, because what emerges is new information. The universe began with minimal information. For hundreds of thousands of years, the only information structures were fundamental particles [from quarks to protons, neutrons, and electrons].

These were only the simplest matter, and they are conserved quantities. In a deterministic universe, that initial information would be all the information in the universe today and in the future, because information would be conserved.

But information is not conserved. Because it is neither matter not energy, information is immaterial. Matter can be converted to energy (E = mc²), but their total is a constant. The only thing that is new is information. Information is the only emergent.

A complex physical world of galaxies, stars, and planets has emerged, a diverse biological world has emerged, and a mental world of ideas has emerged, including the idea of emergence itself. Emergence is the result of the cosmic creation process.

And this process is fundamentally a rearrangement and transformation of the fundamental particles of matter and energy. The basic idea of emergence is that there are properties - perhaps even “laws” - at the upper hierarchical levels of nature that are not derivable from or reducible to the properties and laws of the lower levels. Thus chemistry has properties not derivable from physics, biology has properties not derivable from chemistry, and psychology has properties not derivable from biology.

Great Problems in Philosophy and Physics, chapter 27, Emergence

In his contribution to the 2018 volume reporting on randomness in nature, Ellis proposed an explanation for a third form of causation beyond the chance and necessity of Jacques Monod. Of course the tertium quid explaining human purpose and moral responsibility has been clear since the ancient philosophers, notably Epicurus.

Ellis goes beyond the epistemological randomness of everyday probabilities, e.g., in games of chance, and the supposed collisions of independent deterministic causal chains Epicurus called sumbebekos or "accidental chance." This he calls "chance as ontological indeterminism" based on quantum physics.

He describes the "outcome" of his thinking...

Layers of quantum indeterminateness at the bottom, classically deter­minate causation at higher levels, and indeterminate effects in emergent higher-level structures at the top can embody higher-level organization and meaning through learning processes allowed by adaptive selection.

God's Providence, p. 58

There is no "classically deter­minate causation" or "physical necessity" of course. There is only the statistical or adequate determinism that emerges for large macroscopic objects where quantum indeterminism is averaged over and processes approach statistical certainty because of the law of large numbers.

Ellis argues strongly for the existence of libertarian free will. He thinks it requires something beyond "chance and necessity." Instead, free will - as well as purpose and goal-directed actions - are simply a combination of quantum indeterminism and the adequate determinism in large objects like the mind.

As in our "two-stage model" for free will, quantum indeterminism generates alternative possibilities in the first stage. An adequate determinism in the second stage makes our choices morally responsible.

These two steps are involved in the creation of new information structures since the beginning of time.