Mind uploading speculation and debate often concludes that a procedure described as gradual in-place replacement preserves personal identity while a procedure described as destructive scan-and-copy produces some other identity in the target substrate such that personal identity is lost along with the biological brain. This paper demonstrates a chain of reasoning that establishes metaphysical equivalence between these two methods in terms of preserving personal identity.
by Keith B. Wiley, PhD and Randal A. Koene, PhD
Dr. Keith B. Wiley is a researcher with experience across numerous fields within computer science. He has been involved in the ongoing discussion of philosophical and practical aspects of mind uploading for twenty years. His first book on the subject, A Taxonomy and Metaphysics of Mind-Uploading, was released in 2014 with support from Humanity+ Press. Dr. Wiley’s articles and papers are available at http://keithwiley.com.
Dr. Randal A. Koene introduced the multi-disciplinary field of whole brain emulation and is lead curator of its scientific roadmap. He is Founder of the foundation Carboncopies.org and President of NeuroMem Inc. Dr. Koene’s publications, presentations and interviews are available at http://randalkoene.com.
Two of the most popular thought experiments in mind uploading philosophy are gradual in-place replacement and destructive scan-and-copy. The former consists of steadily replacing individual components of the brain, say neurons, with microscopic devices of functional equivalence, while the latter stabilizes the brain via vitrification or plastination, then sections and scans the static brain, and then instantiates the scan via whole brain emulation (WBE) in a computational substrate.
A popular conclusion after considering these scenarios is to view gradual in-place replacement more favorably than scan-and-copy with regard to successfully preserving or transferring personal identity. Gradual replacement is granted the status of successful identity preservation while scan-and-copy is denigrated as producing a copy, i.e., some other person, while the mind entering the procedure died [Corabi & Schneider 2012, Dorrier 2015, Hay 2014, Josh 2009, Morris 2013, Schneider 2014]. We propose that both scenarios should actually be considered metaphysically similar in the ultimate identity status of the minds they produce, either successful transfer preserving personal identity or failure producing some other. We first equate slow gradual in-place replacement (SGR) with quick gradual replacement (QGR) or even instantaneous replacement (IR) (all neurons are replaced simultaneously at the flip of a master switch), and then equate IR with destructive scan-and-copy (SaC). This reasoning establishes a transitive relation connecting SGR, IR, and SaC, the implication being that all three procedures should receive the same identity status, ostensibly successful transfer preserving personal identity.
Parameters and Assumptions of the Discussion
We substitute the term identity preservation for the common notion of transferring identity from one brain to another, and we substitute the emergence of some other identity for the common notion of copying an identity, which implies metaphysical failure to transfer the mind and personal identity, and further that the mind that entered the procedure died. We avoid transfer due to its overly spatial implications and we avoid copy because it is broadly used in other ways, e.g., copying a mind, personal identity, neural functionality, cognitive state (knowledge, memories, personality, etc.), brain scan data, physical brain structure or material pattern, etc. It appears in the popular label for the mind uploading method known as scan-and-copy, but there expresses purely technical aspects of data copying and does not speak to identity preservation one way or the other.
To clarify a possible point of confusion, we are not considering whether there are valid practical or strategic reasons to choose one procedure over another. For example, we are not considering whether gradual in-place replacement has a physiological and technical speed limit, i.e., whether replacement above a certain rate might yield an upload that fails to adequately preserve neural functionality and cognitive behavior, and thereby fails to sufficiently resemble the person who entered the procedure. Nor are we are considering whether SaC has technical transfer distance limits (e.g. teleportation, a variant of SaC) due to unreasonable energy requirements for perfect signal transmission across vast distances. Practicalities of technical efficacy are irrelevant to this philosophical discussion precisely because detractors often grant this concession when denying identity status to an uploaded individual. The spirit of the it’s-just-a-copy claim is that even if perfect preservation of function is achieved, we should nevertheless regard the person as dead and refuse to grant the uploaded mind the same personal identity. We are only considering whether metaphysical identity is subject to some transition from preserved to other personal identity. Technical efficacy is off the table.
In this article, we do not consider that some theories of identity might allow blends of preservation and other identity (while other theories certainly might not). We focus on a related concept, survival, which is a discrete judgement of success vs. failure [Chalmers 2010]. As to whether the person entering an uploading procedure explicitly survives to then associate with the new substrate, or dies with the biological substrate, we should draw a discrete conclusion in any given scenario. Central to the it’s-just-a-copy argument and its dismissal of the identity status of an upload, survival is actually the paramount concern, and an intermediate conclusion on survival quite simply betrays the meaning of the word. Consequently, we needn’t consider smooth transitions of identity in so far as such nuances do not extend to the underlying survival, the actual primary concern.
It is important to clarify our stance on nondestructive uploading, i.e., the paradox of allowing transfer of identity in a SaC scenario that does not destroy the biological brain and mind, a possibility this article does not discuss at length. Some readers, and most detractors on the question of transfer status in SaC, take this paradox as proof in itself that identity transfer is simply beyond the pale in any SaC scenario. We propose that the best solution to the paradox of mind uploading in which the biological brain survives (including under-appreciated variants of SGR in which the brain survives [Wiley 2014]) is to adopt a completely different third model of identity that conforms to neither the transfer (preservation) nor the copy (other) interpretation, but rather to the notion that minds and personal identity can conceptually split into multiple descendants of equal primacy to their common ancestral mind and identity. A thorough description of this recommended identity model will not fit here, but please see Cerullo  or Wiley  for detailed descriptions. To simplify the question of identity preservation vs. other, this article considers only procedures in which a single mind enters and a single mind exits, and then inquires whether the mind that entered explicitly survived.
Equating Slow Replacement with Quick Replacement
Consider a spectrum of temporal rates of gradual replacement, measured in neurons replaced per second or some comparable metric (see scenario 22.214.171.124.1 of the taxonomy in Wiley  for a detailed description). Slow, incremental replacement is how gradual replacement is generally presented (Both [Wiley 2014] and the full paper this article summarizes question the slowness of QGR, but we forgo the details here) and in this way it differs from SaC, which equates to global instantaneous (or at least discontinuous) identity transfer. At faster replacement rates, SGR approaches QGR or even IR, thereby resembling SaC in some crucial aspects.
Some readers may assume that faster replacement rates fail to transfer identity, with some other person resulting from the upload process and the one who entered the procedure having died. For example, SGR is often hailed for maintaining some notion of a stream of conscious continuity [Chalmers 2010, Van Gulick 2014]). In it’s-just-a-copy debates, arguments that nongradual procedures fail to transfer this purported stream are often raised. However, defending such a conclusion falls to its proponent—perhaps the alleged conscious stream can survive quick or instantaneous replacement after all, obviating this challenge, or perhaps the entire idea of a consciousness stream is simply flawed [Blackmore 2002, Dennett 1991]). For readers who would grant preserved identity to QGR and IR, but who would nevertheless deny it to SaC, we address that view in the next section.
To hold the position that slow replacement preserves identity but that quick replacement does not implies that a success-to-failure transition resides somewhere on the spectrum of replacement rates, a cutoff where personal identity preservation flips to producing some other identity. Immediately below the cutoff, replacement would be sufficiently slow to allow total preservation of personal identity, yet at an infinitesimally faster rate, the interpretation would be to utterly reject metaphysical transfer or preservation, resulting in some other identity instead. While all mental functionality would still technically transfer to the new substrate (as clarified above), thereby producing an identically functioning, thinking and behaving person, detractors would apparently claim that the crucial properties of personal identity have failed to ride along, and for no better reason than the minutest increase in replacement rate. The proposal of such a cutoff requires explanation, much less some notion of where on the replacement rate spectrum it actually resides, and the default position, absent a solid theory to the contrary, should be that no such state-change occurs.
Some readers might propose that the transition from identity preservation to other identity be not necessarily discrete, but rather a smooth continuum cross-dissolving from full preservation in SGR to full other in QGR or IR, with intermediate replacement rates producing a mixture of preservation and other. However, as stated above, we are focused on the practical concern of discrete survival, not the possibility of theories of identity that might enable blends of preservation an other identity proportional to the replacement rate. Consequently, for there to be survival in SGR but death in QGR or IR requires a discrete cutoff of the most infinitesimal change in replacement rate, a seemingly unlikely proposition.
If we conclude that no transition is ultimately defensible and we grant transfer status to an IR individual, then if there is also subsequently no meaningful difference between IR and SaC, we should grant transfer status to SaC as well. This reasoning results in a conundrum for the position that SGR and SaC should receive differing survival statuses. The realization of this inconsistency is the crux of this article. Having argued against the temporal distinction between SGR and SaC, the only remaining distinction is that SaC may involve a larger spatial translation from the biological brain to the new substrate, an argument which we consider next.
Equating Quick Replacement with Destructive Scan-and-Copy
Some readers may feel that the distinction between IR and SaC lies in the likelihood that SaC involves a greater spatial translation of neural function from the biological brain to the new substrate, perhaps even on the belief that in-place replacement involves no spatial translation at all. In these debates it is sometimes asked how function and identity could possibly move through space from one brain to another. It may seem that minimizing or even negating any spatial translation of the neural functionality and metaphysical mind implies greater compatibility with identity preservation, especially as contrasted with spatially transferring a person’s mind and identity across a room to a cloned or robotic body. However, this position is difficult to rationalize.
First of all, the possible assumption that in-place replacement involves no spatial translation is simply incorrect. While scenario 126.96.36.199.2 in the taxonomy presented in Wiley  offers a detailed explanation, the following summary is straightforward. As a neuron hands off its neural behavioral role to a nearby microscopic device, there is always a spatially discontinuous translation of function from location A to B (in so far as we can speak of nonphysical functionality residing at a location in space or moving through it in the first place!). At one moment, some neural function is being performed by a biological neuron; then at some later time that same function is being performed by a nearby artificial neuron in a different location and the biological neuron is no longer operational. The two entities, a neuron and its replicant, cannot spatially coincide even if they physically abut (~10–100 microns from center of neuron to center of replicant).
We can then consider whether there remains a fundamental difference in this nonzero translation between the two scenarios. In SGR, the distance over which functionality purportedly transfers is microns. In SaC, this distance is generally meters (across a room) but could be kilometers—or even light-years (e.g., teleportation, a variant of SaC). Consequently, any spatial distinction must now hinge on distance comparisons. Curiously, Wiley  shows that the micron-scale per-neuron translations involved in in-place replacement accumulate thousands of kilometers of discontinuous spatial translation of function, despite the possible presumption that no spatial translation is involved. Once we have already accepted spatial transfer of function over thousands of kilometers—albeit distributed over billions of neurons—what difference does a few meters across a room really make?
The spatial translation issue leaves us with two possible conclusions. We can declare that translations below some distance threshold permit preservation of identity while farther translations are deemed preservation failures (and furthermore invoke producing another mind while at shorter distances, apparently no other is created!), or alternatively, we can accept translations of any distance as being functionally and metaphysically equivalent. As with a temporal cutoff, the problem is to show how identity preservation can suddenly change to other identity, at what distance the cutoff resides, and what possible metaphysical property could tie identity preservation and spatial translation in distance-dependent ways (including vast accumulations gathered over numerous microscopic translations, as shown above). Additionally, the distinction between personal identity and survival applies here as well: to propose a smooth transition blending preserved and other identity relative to the distance translated from the biological brain to the new substrate is to miss the point that discrete survival is the fundamental concern.
Bear in mind that the counterproposal that the distinction lies in piecewise replacement, not distance, puts us right back in the temporal issue all over again. What could possibly be the nonphysical property of consciousness and personal identity survival that is subject to these physical and spatial effects? Until solid theories are established on such questions, the default philosophical stance should be the simpler theory, namely to entirely dispense with translation-distance-dependent identity. Furthermore, doesn’t it seem remarkably suspicious that in such pondering we are tempted to assign a cutoff such that distances we can’t easily distinguish in our daily experience (microns) are considered safe while distances we casually comprehend as distinct translations (meters and beyond) are considered unsafe? Such a designation is anthropocentric. Would aliens who are a few orders of magnitude smaller or larger than humans assign this cutoff differently?
If both the temporal (SGR to IR) and spatial (IR to SaC) distinctions fall, we then equate SGR with SaC, thereby concluding that all these scenarios are functionally equivalent. This conclusion does not prove that SaC must be regarded as a successful transfer of personal identity, but it does demonstrate that both procedures should be judged in the same manner: we either grant SaC successful status and stop denigrating it as a mere copy lacking in proper identity status, or we refuse to grant identity status to the oft-favored SGR and deem both procedures to be metaphysical impossibilities.
Toward resolving this final question, the general notion of identity appears to tolerate piecewise replacement, spatial translations, and even whole parcel SaC. While the classic thought experiment of The Ship of Theseus merely poses as an open question whether identity can survive piecewise replacement, many conceptually identical examples are taken for granted to do so, such as our own bodies, in which very little matter persists over the long term, waves in any physical medium, colonies, etc. With regard to SaC, multiple copies of a book or recordings of a song are casually regarded as multiple physical instantiations of a singleton information pattern (even in this very sentence we referred to the book and the song in singular vernacular, and all readers, including detractors on our central issue, accepted that phrasing without even noticing the irony). In other words, we apply the word copy to the physical instance of a book while recognizing that the underlying physically embedded information has neither duplicated nor even really changed location in a meaningful sense; those are properties of the physical instantiation, not the associated information. All of these examples suggest that we should indeed grant a status of preserved personal identity to SGR, IR, and SaC.
Note: This article is an op-ed version of a longer paper currently under peer-review. Please refer to the preprint, available at http://arxiv.org/abs/1504.06320 (in addition to Philica, SSRN, and Cogprints), for a more detailed presentation.
We would like to thank Michael Cerullo, Alexander McLin, and Oge Nnadi for their collaboration on this topic and on refining and editing this paper.
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