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Suppose I'm a inland, rural, tropical farmer who spend my life in one place tending to my farm without education in astronomy. Then someone comes along and tells me that the earth is round. All the "proofs" he tells me don't seem to be very convincing.

  • Ships disappearing on a horizon? I live inland, never seen such a thing!
  • Circumnavigation? Timezones? That's just tales people say, never experienced those myself in my farm!
  • Shadow of the earth looks round during a lunar eclipse? Well that assumes a specific account of the lunar eclipse (i.e. that it occurs when the moon passes in the earth's shadow), why would I believe that?
  • Somebody flew to outer space and took this picture? Are you kidding me!

Besides, believing whether the world is flat or round doesn't seem to affect my life enormously. I'm just a farmer.

It seems the simpler explanation is what seems obvious from looking around me, which is that the place I live in seems to be a plane, not a sphere. Believing that it is round requires much more assumptions, for example, a specific account of the lunar eclipse, or the possibility of space travel and the genuineness of this 'round earth' photo that people show me.

Does it mean that in this scenario, I'm justified in believing that the earth is flat?

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    If you are indeed "just a farmer", it seems unlikely that you would even know what Occam's razor is, much less how to use it to win an argument. The degree of intellectual sophistication required to articulate an argument like, believing that it is round requires much more assumptions requires a mind that is acquainted to the reasons why we should believe the Earth is round - and to the reasons why we should take those reasons as valid. – Luís Henrique Jul 13 '16 at 11:21
  • The history of science shows that modern scientific theories are much more complex than older ones (comapre quantum mech with Aristotelian natural phil): the issue is that modern sc.th are able to explain much more "facts" and more complex than previous ones. – Mauro ALLEGRANZA Jul 13 '16 at 12:04
  • @LuísHenrique Sure I wouldn't probably know the term Occam's razor or use well-formulated arguments, but it doesn't mean I wouldn't (for pragmatic or other reasons) pick an easier/simpler out of several alternative explanations that work for me. – user69715 Jul 13 '16 at 13:21
  • @MauroALLEGRANZA Yes, but my point is, my hypothetical farmer wouldn't need or even encounter the higher explanatory power of the round world theory. Perhaps roughly similarly, one who doesn't have a highly technical job or activity would probably be OK to just believe in Newtonian mechanics - they wouldn't encounter the special cases where the explanatory powers of relativistic mechanics are needed – user69715 Jul 13 '16 at 13:29
  • But we do not believe that "the earth is round" because we have a proof of it; we believe it because the experts says so. – Mauro ALLEGRANZA Jul 13 '16 at 14:05
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If in fact your farmer is constrained to always be within a few miles of his home (vertically too), then to within a few feet of elevation (which is probably swamped by topography anyway) the Earth is flat. If the roundness of the Earth never affects him/her then that is all he/she needs to know, and the (local) evidence provides justification for this.

What ends up being unjustified is a committed belief that this local model applies globally.

In my view, there is no Occam's Razor issue here; this is all about what range of phenomena need to be explained, and what evidence apply to it.

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    Interesting. So what you're saying is the farmer is justified in believing that "the world" (the farmer's location and whatever can be observed from there) is flat, but he/she needs more justification if he/she wants to claim that Beijing, New Delhi, New York and Jakarta (if he/she knew these places) are all in a plane? – user69715 Jul 14 '16 at 0:22
  • This earth is not a flat plane. Like you said, it has topography. The earth is not a sphere either. Planes and spheres are constructs of the imagination used to describe and calculate. They don't exist in nature in the strictest sense of the definition of the words. Put some water on a ball, throw it with a spin. Does the water cling to the ball or fly off? Well that's the experiment to test the theory isn't it? – ejbytes Apr 20 '17 at 7:22
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Well, this depends on what you mean by "justified"; it is understandable that a person like you describe in your question would doubt that the Earth is a sphere; that doesn't make her right, though.

One is justified in being skeptic of any accounts that seem to go against common sense and common experience, but one is not justified in presuming that their particular set of experiences should prevail over the experiences of others. If someone comes to me and tells something like, "in Turkey women are forbidden from walking on the streets without male company", I am entitled to doubt this until more evidence is given; I am not entitled to an argument from ignorance, such as "I have never seen or heard of any place where such a rule holds, consequently the claim is false". I am entitled, however, to ask something like, "yes? In this case, who buys groceries for the house?" (Or, of course, to google for "Turkish women walking alone on streets", which would by the way quickly dispell the whole xenophobic tale.)

Similarly, your farmer is entitled to ask, "if the Earth is really a sphere, how does it happen that things don't slide and fall from it?". He's also entitled to dispute your evidence. Yes, boats may disappear in the horizon (and then come back, proving that they didn't simply sink), but this is compatible with many Earth configurations besides a sphere; Earth could be, say, a paraboloid. It isn't reasonable, though, to argue that people must be lying about circumnavigation or space travel - here Occam's razor would start working against the hypotethical farmer; the complexity of a theory that explains why people would lie about such an issue is probably much greater than the complexity of gravitation. The farmer could be still "justified", in the sence that his surprise is understandable, if this is the first time he hears about it; his skepticism isn't justifiable if his children's school, the TV, the books he access to, the internet, are all agreeing that the Earth is a sphere.

Plus, Occam's razor should be used when theorising about a set of given facts, which are no longer under discussion. We know that things fall to the ground, or anyway to the nearest surface below them. There is no dispute about that fact. Now philosopher X theorises that this is because angels push things down. Occam's razor should be used to shave this hypothesis out, because entia non sunt multiplicanda praeter necessitatem, and philosopher X is creating an entity (angels) that aren't necessary to explain why things fall (as everybody since Aristotle knows, this happens because things have a natural place according to their composition, and things predominantly made of earth have a lower natural place than things predominantly made of water, or air, or fire...)

But when the facts are in dispute, we would need a different razor; Occam's doesn't trim that kind of hair. If the farmer denies that boats disappear in the horizon without sinking, we will need to show him this curious fact (or he will need to show us that boats in fact do not disappear in the horizon), which is something Occam cannot help us with, at least not if only armed with his razor.

The problem, of course, is that not all people have access to all facts. A hunter gatherer living in the Magdalenian culture would not have the necessary information about ships disappearing in the horizon, much less circumnavigation or photographs of the Earth taken from space. His shaman would perhaps have noticed that the shadow in the Moon during an eclipse looks like an arc of circle (though he would probably not realise it was the Earth's shadow), but the common warrior/hunter would have probably never noticed it. So his ignorance would be historically "justified"; we do not know things that we cannot know due to the technological historical constraints we are subjected to. An Athenian philosopher, or even an Athenian sailor, would be much less justified; they already knew about disappearing ships, and the philosopher at least would certainly understand that an eclypse is caused by the Earth coming between Moon and Sun (that would be known at least since Babylonian astrologers investigated the issue); moreover, the Greek philosopher would know of a much better argument for the sphericity of Earth than disappearing ships, circular shadows, circumnavigation, or space photos, which I discuss below.

The way it was first demonstrated that Earth is a sphere was by measuring shadows. Greek philosophers measured the shadow of some standard object at about the same time (at least, the same day) in different places (Alexandria and Athens, IIRC), and those shadows have a different lenght that can be only explained if the Earth's surface is curve (they assumed, I think, that such curve was a sphere, out of superstitious beliefs about spheres being "natural" or "perfect" solids; but the experience can be repeated by measuring shadows in more than two different places, and in this case other curved surfaces would be necessarily dispelled out of simple geometrical calculations). This is a much better argument, because anyone with the necessary foreign contacts and communication tools can repeat the experiment at a desired time (while eclipses are time consuming to say the least, circumnavegation and space photos require technological advances only available much later, and disappearing ships do not demonstrate much more than a generic curvature that could even be merely a local phenomenon).

  • There are other assumptions that need to be accounted for which exponentially and infinitely make the round earth model that much more complex - for example, in order to justify a round earth, one must accept the complex principle that created the round earth stemming to the big bang theory to the universes infinite expanse. Surely that is not the simplest of the two models. – Kraang Prime Dec 12 '17 at 4:24
  • @KraangPrime - Why? We have accepted the round earth model for two millenia, even though we only developed big bang theory a few decades ago. It is perfectly compatible with geocentrism, creationism, or a limited spheric universe contained within a blue sphere called sky. – Luís Henrique Dec 12 '17 at 23:40
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Stronger than "justified in believing" you are justified in stating it as a fact and as a matter of great concern.

The statement "Earth is known to be a fixed plane." is justified by no evidence of curvature, physics explained with of EM and buoyancy with no need of a "force of gravity", and star cycles & eclipses predicted by our ancestors all still work.

The admission is made by astronomers themselves that our observations can be explained both by heliocentric & geocentric/fixed-plane frames of reference.

Here is the admission related to the cosmic microwave background radiation images from 2003 & 2013. "While this might suggest that Earth is at the center of the universe, the Copernican principle requires us to interpret it as evidence for the evolution of the universe with time..." https://en.wikipedia.org/wiki/Copernican_principle

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