undefined | Better HN

0 pointstsimionescu1mo ago0 comments

I wasn't trying to use that as a definition of what computation means. My point is that regardless of how we define it, the fact is that the devices we build to do some form of computation are objectively successful at doing what they were built to do.

For example, you can say that Firefox is a human-centric abstraction, and that my computer isn't running Firefox right now in an objective sense, that this is is just a human-centric interpretation of what the physical device is doing, and that there exist other computations that we could assign to it.

But what you can't say is that the device is not affecting the physical world in ways that are consistent with performing the Firefox computation, such as causing certain specific wavelengths of light to be emitted by the screen based on state that is stored in a server in the YCombinator data center. This is a measurable fact of the physical world that is independent of the model of computation you chose to ascribe to the physical device - any consistent mapping will have to preserve this same physical property.

0 comments

3 comments · 1 top-level

bch8_1mo ago· 2 in thread

The paper addresses this point in section 3.2. They aren't debating the fact that a physical process is taking place in a computer running a program. They are arguing that the semantic interpretation of the output of that program is indeterminate and dependent on the mapping function:

> A single physical vehicle (bottom) possesses a fixed causal trajectory. However, it does not instantiate a unique computation. Depending on the alphabetization key applied (fA or fB ), the same physical states can be mapped to entirely different abstract computations (Top Left vs. Top Right). Therefore, computation cannot be intrinsic to the physics (p).

So yes there is a physical process generating your Firefox browser, but there is also a mapping function taking that program and interpreting that it should display your Firefox browser. There are any number of mapping functions that could be applied to the physical state in order to display other things on your screen besides the browser. Therefore, the Firefox browser being displayed is not inherent or intrinsic to the physical state of your computer. If we did not have the right mapping function, we would have no way of knowing or inferring or discovering which mapping function is correct.

tsimionescuOP1mo ago

But the results that the computer screen shows, and the inputs fed into the machine, are entirely physical, observer-independent processes. Just like an inscribed papyrus contains letters in a physically observable, provable sense - even if the semantics of those letters are entirely man made.

This is in fact very similar to the notion of text - text is a physical medium, that provably contains a message that one human intended to convey to other humans. The same physical text can be interpreted in an infinite number of ways, and they are all equally valid in that they are self-consistent, but only one is the intention of the original author.

bch8_1mo ago

To the best of my understanding I believe the response from the position taken by the paper is that this is still committing the abstraction fallacy (Assuming you aren't just agreeing with them here, which I don't think you are). The book itself doesn't physically instantiate the information it contains in its text. In a vacuum it is informationally inert. That doesn't mean it doesn't physically exist. Likewise the computer running Firefox obviously physically exists. The fallacy is the next jump from there - assuming that the semantic content of the book or software is physically present in those items. Another example given in the article is an analog clock:

> Consider an analog clock. Physically, the device is a collection of gears and springs governed by continuous dynamics (P). It only “computes” time because a mapmaker intervenes, mapping a specific set of continuous angles to a semantic concept (e.g., “3:00 PM”). Without this semantic imposition, the clock is just metal moving in accordance with Hamilton’s equations; it contains no intrinsic “time.” Thus, the physical substrate does not “process information” absent a prerequisite alphabet of intrinsic symbols; rather, it generates continuous dynamics that an external mapmaker interprets as information.

In this example the time "3:00 PM" is instantiated in the mind of the person reading the clock, it is not a real physical property of the clock itself.

2 more replies

j / k navigate · click thread line to collapse