- "Precursors felt the Mantle extended to the entire universe, energy and matter as well as living creatures ... some say. The universe lives, but not as we do."
- — Bornstellar Makes Eternal Lasting explaining the premise of neural physics.
Neural physics was a Precursor concept which posited that the Mantle encompassed the entire universe, including living beings, energy and matter. The principles of neural physics also postulated that the entire universe was living, but in a way that was beyond the comprehension of biological organisms. Blurring the line between philosophy and science, neural physics was not a mere belief to the Precursors as transsentient entities. They were able to harness its principles as a transcendent form of technology, used to create solid structures or travel the stars. The workings of neural physics were completely beyond the conventional technologies of younger races, even the Forerunners, the most technologically adept civilization since the downfall of the Precursors themselves.
Drawing from an exotic neurophysical energy permeating the cosmos, the Precursors made their artifacts effectively indestructible, allowing them to exist for millions or potentially billions of years without decay. As such, evidence of the Precursors' mastery of neural physics remained in the galaxy after their disappearance, in the form of star roads and many other vast, effectively eternal structures. In a concept later echoed by the Forerunners in their philosophy of Living Time, the Precursors cherished the interaction of living beings with the universe, all individual experience adding to the totality of a transcendent universal wisdom. To record and retain these life-patterns for all of time, the Precursors created the Domain, a metaphysical, ever-changing library of the collective experiences of living things, stored in neural physics architecture within the Milky Way galaxy.
In the final years of the Forerunner-Flood war, it was revealed that the Flood was able to control the Precursors' neural physics artifacts. After the proliferation of planet-sized Key Mind forms, the Flood compound mind, itself of Precursor origin, had amassed enough beings to elevate its intelligence to a state of transsentience, enabling it to use its vast mental capacity to access the neural architecture. The Flood also began to utilize neural physics-based Precursor superluminal travel, which made slipspace unsuitable for Forerunner drives on an interstellar scale. This form of travel used an exotic form of causality compensation evidently unlike the reconciliation the Forerunners relied on, although the principles of this mechanism were wholly unknown to the Forerunners. Ships using neural physics transit would shed multiverse residues relatively slowly upon returning to normal space, rendering them momentarily vulnerable. This manifested visually as an aura of purple radiation surrounding the object undergoing the transmission. In one known instance, the Forerunners were able to exploit this weakness: catching the Flood fleet by surprise, the Forerunners flung asteroids at the arriving ships. While the Flood vessels could save themselves by repositioning by several thousand kilometers, many were disintegrated as the incoming asteroids abruptly merged with the ships' mass upon passing into their emergence fields.
The nature of neural physics construction made Precursor architecture susceptible to the effects of the Halo Array, which specifically targeted neural systems. When a Halo was tested near Charum Hakkor, the weapon's effect negated neural physics within the region and shattered every Precursor structure on the planet. Likewise, the Halos' activation at the conclusion of the Forerunner-Flood war destroyed all neural physics-based architecture in the galaxy.
A select few non-Precursor technologies utilize neural physics; the only known Forerunner creation to do so is the Composer, a form of sublimation device capable of emitting high-energy fields that resonate with any neural structure in range and effectively convert biological bodies and mental content into digital format in a process not truly understood even by the Forerunners themselves.
The premise of neural physics is similar to panpsychism, the philosophical concept that mind or soul is a fundamental aspect of everything that exists.
List of appearances
- Halo: Cryptum, page 103
- Halo: Silentium, page 40
- Halo: Cryptum, page 267
- Halo: Primordium, pages 365, 367
- Halo: Silentium, pages 322-323
- Halo: Silentium, pages 186-187
- Halo: Silentium, pages 111
- Halo: Silentium, page 231
- Halo: Silentium, page 213
- Halo: Silentium, page 326
- Halo Waypoint: Composer