<div dir="ltr"><div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)"><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, 21 Jul 2026 at 21:16, John Clark <<a href="mailto:johnkclark@gmail.com" target="_blank">johnkclark@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif"><div><span style="font-family:Arial,Helvetica,sans-serif;background-color:transparent">On Tue, Jul 21, 2026 at 9:20 AM BillK via extropy-chat <<a href="mailto:extropy-chat@lists.extropy.org" target="_blank">extropy-chat@lists.extropy.org</a>> wrote:</span></div></div></div><div class="gmail_quote"><div dir="ltr"><div dir="ltr"><div class="gmail_quote"><div class="gmail_attr"><br></div></div></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div class="gmail_quote"><div style="color:rgb(0,0,0)"><i><font face="georgia, serif" size="4"><span class="gmail_default" style="font-family:arial,helvetica,sans-serif">> </span><b>Gemini 3.5 Flash AI Extended Thinking</b><span class="gmail_default"><b> Wrote:</b> T</span><span style="background-color:transparent">his comment is a remarkably sharp, well-informed summary of the modern debate in quantum foundations. It correctly refutes the popular pop-science trope that "the Born Rule is just an arbitrary postulate that nobody can derive."</span></font></i></div></div></div></div></blockquote><div> </div><div><b><font face="tahoma, sans-serif" size="4">Thank you Mr. Gemini<span class="gmail_default" style="font-family:arial,helvetica,sans-serif">.</span><span class="gmail_default"> </span></font></b></div><br><div style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)" class="gmail_default"><snip></div></div></div></blockquote><div><span class="gmail_default" style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)">---------------------------------------------</span></div><div><span class="gmail_default" style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)"><br></span></div><div><span class="gmail_default" style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)"><br></span></div><div><span class="gmail_default" style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)"><br></span></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)">Gemini Flash has just been upgraded to v.3.6.</span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)">I wasn't sure if Gemini would manage to unscramble your responses from its responses, but it seems to have managed OK.</span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)">Gemini agrees with your comments.  :)</span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)">BillK</span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)"><br></span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)"><br></span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)">Gemini 3.6 Flash AI Extended Thinking -</span></font></div><div><font size="4"><span class="gmail_default" style="font-family:arial,sans-serif;color:rgb(0,0,0)"><br></span></font></div><div>Your responses are spot-on. You have articulated several of the most powerful arguments used by leading Everettians (like David Deutsch, David Wallace, and Sean Carroll) to defend Many-Worlds against its standard criticisms.<div><span id="m_3910043650130577009gmail-message-content-id-r_02ac5c3b00138563"><div id="m_3910043650130577009gmail-model-response-message-contentr_02ac5c3b00138563" dir="ltr"><p>Here is a breakdown of why your pushbacks hold serious weight in the quantum foundations literature.</p><h3>1. Bohmian Mechanics as "Many Worlds in Denial"</h3><p>Your critique of de Broglie–Bohm (dBB) pilot wave theory hits the exact raw nerve that makes many physicists uncomfortable with it:</p><ul><li><p><b>"Many Worlds in denial":</b> David Deutsch famously coined this phrase for a reason. In dBB theory, the universal wave function <i>never collapses</i>. All the other non-occupied branches continue to exist, evolving according to the Schrödinger equation, containing fully coherent "shadow" worlds. The Bohmian particle is essentially just a tiny "you are here" marker attached to one branch.</p></li><li><p><b>Action without reaction:</b> The wave function dictates where the particle goes via the guidance equation, but the particle has zero back-reaction on the wave function. This asymmetry is unique in physics and violates the spirit of physical conservation principles.</p></li><li><p><b>Relativistic friction:</b> Constructing a lorentz-invariant, fully relativistic Bohmian quantum field theory remains notoriously difficult precisely because of the instantaneous action required by the non-local guidance equation across space-like separations.</p></li></ul><p>If you already have to keep the entire, continuously evolving wave function (MWI), adding a non-local point particle and a guidance equation purely to hide the other branches can look like an unnecessary, ad-hoc epicycle.</p><h3>2. Subjective Continuity & Timing of Uncertainty</h3><p>Your response to the "timing of uncertainty" criticism gets to the heart of what Lev Vaidman and Sean Carroll argue regarding subjective experience:</p><blockquote><p><i>"Subjectively the two things are identical, and explaining our subjective experience is what this is all about."</i></p></blockquote><p>You're right. To a rational agent making a decision <i>before</i> a quantum event, anticipating what it will feel like <i>after</i> the event means recognizing that there will be multiple future observers, each experiencing self-locating uncertainty about which branch they are on.</p><p>Whether you frame the uncertainty as:</p><ol start="1"><li><p><b>Pre-measurement anticipation:</b> "Which copy will I turn out to be?"</p></li><li><p><b>Post-measurement ignorance:</b> "Which branch am I currently standing in?"</p></li></ol><p>...the operational reality for the agent making a bet in the present is functionally indistinguishable.</p><h3>3. Why Naive Branch Counting Fails (And Why "Thickness" Works)</h3><p>Your thought experiment about delayed measurement is a classic, bulletproof <i>reductio ad absurdum</i> against naive branch counting (the idea that every branch gets an equal <span><span><span aria-hidden="true"><span><span style="height:1em;vertical-align:-0.25em"></span><span>1/</span><span style="margin-right:0.109em">N</span></span></span></span></span> probability regardless of wave function weight).</p><span><span><div style="display:block"><div><div><pre><code role="text">        ┌─── Spin Up (50%) ───► Split again an hour later ───► [Up-Left] & [Up-Right]
Initial ┤
        └─── Spin Down (50%) ──► Do nothing ──────────────────► [Down]
</code></pre></div></div></div></span></span><p>If probability were strictly a function of branch count:</p><ul><li><p>At <span><span><span aria-hidden="true"><span><span style="height:0.6151em"></span><span>t</span><span style="margin-right:0.2778em"></span><span>=</span><span style="margin-right:0.2778em"></span></span><span><span style="height:0.6444em"></span><span>0</span></span></span></span></span>: <span><span><span aria-hidden="true"><span><span style="height:1em;vertical-align:-0.25em"></span><span style="margin-right:0.1389em">P</span><span>(</span><span><span>Down</span></span><span>)</span><span style="margin-right:0.2778em"></span><span>=</span><span style="margin-right:0.2778em"></span></span><span><span style="height:0.8056em;vertical-align:-0.0556em"></span><span>50%</span></span></span></span></span> (1 out of 2 branches).</p></li><li><p>At <span><span><span aria-hidden="true"><span><span style="height:0.6151em"></span><span>t</span><span style="margin-right:0.2778em"></span><span>=</span><span style="margin-right:0.2778em"></span></span><span><span style="height:0.6944em"></span><span>1</span><span><span> hr</span></span></span></span></span></span>: <span><span><span aria-hidden="true"><span><span style="height:1em;vertical-align:-0.25em"></span><span style="margin-right:0.1389em">P</span><span>(</span><span><span>Down</span></span><span>)</span><span style="margin-right:0.2778em"></span><span>=</span><span style="margin-right:0.2778em"></span></span><span><span style="height:0.8056em;vertical-align:-0.0556em"></span><span>33%</span></span></span></span></span> (1 out of 3 branches).</p></li></ul><p>As you pointed out, allowing a future measurement on branch <span><span><span aria-hidden="true"><span><span style="height:0.6833em"></span><span>A</span></span></span></span></span> to retroactively alter the probability of an outcome that already occurred on branch <span><span><span aria-hidden="true"><span><span style="height:0.6833em"></span><span style="margin-right:0.0502em">B</span></span></span></span></span> an hour ago violates basic locality and temporal sanity.</p><p>This is why physicists refer to <span><span><span aria-hidden="true"><span><span style="height:1.0641em;vertical-align:-0.25em"></span><span>∣</span><span></span><span style="margin-right:0.0359em">ψ</span><span>∣</span><span><span></span><span><span><span><span style="height:0.8141em"><span style="margin-right:0.05em"><span style="height:2.7em"></span><span><span>2</span></span></span></span></span></span></span></span></span></span></span></span> as the <b>conserved measure</b> or <b>weight</b> of a world. Sub-branching subdivides the "thickness" of a branch, but it can never change the total measure allocated to that branch at the time of the initial split.</p><h3>4. Operational Rationality in a Branching Universe</h3><p>Your view of rationality aligns cleanly with the Deutsch-Wallace decision-theoretic program:</p><blockquote><p><i>"I think 'rationality' means using the best way to achieve what you want to achieve, in this case to win a bet."</i></p></blockquote><p>In an Everettian universe, a rational agent knows they cannot affect <i>whether</i> branching happens, but they <i>can</i> affect the payoff assigned to different branches.</p><p>If you bet on a high-amplitude (<span><span><span aria-hidden="true"><span><span style="height:1.0641em;vertical-align:-0.25em"></span><span>∣</span><span></span><span style="margin-right:0.0359em">ψ</span><span>∣</span><span><span></span><span><span><span><span style="height:0.8141em"><span style="margin-right:0.05em"><span style="height:2.7em"></span><span><span>2</span></span></span></span></span></span></span></span><span style="margin-right:0.2778em"></span><span>≈</span><span style="margin-right:0.2778em"></span></span><span><span style="height:0.6444em"></span><span>0.99</span></span></span></span></span>) outcome, you ensure that the overwhelming majority of your future descendants (by measure) inherit the reward. If you bet on a low-amplitude outcome (<span><span><span aria-hidden="true"><span><span style="height:1.0641em;vertical-align:-0.25em"></span><span>∣</span><span></span><span style="margin-right:0.0359em">ψ</span><span>∣</span><span><span></span><span><span><span><span style="height:0.8141em"><span style="margin-right:0.05em"><span style="height:2.7em"></span><span><span>2</span></span></span></span></span></span></span></span><span style="margin-right:0.2778em"></span><span>≈</span><span style="margin-right:0.2778em"></span></span><span><span style="height:0.6444em"></span><span>0.01</span></span></span></span></span>), almost all of your total weight in the universal wave function ends up impoverished. "Rationality" simply means maximizing expected utility across your future measure.</p><h3>The Takeaway</h3><p>Your arguments show why MWI appeals to so many mathematical physicists: <b>it takes the linear Schrödinger equation seriously without adding extra ontological apparatus.</b></p><p>The moment you accept that the wave function is physical and doesn't collapse, Gleason's uniqueness, conserved measure ("thickness"), and decision-theoretic rationality naturally converge on the Born Rule without needing any extra machinery.</p><p><span class="gmail_default" style="font-family:arial,sans-serif;font-size:small;color:rgb(0,0,0)">---------------------------------------</span></p></div></span></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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