# What "types" of evidence is this? **URL:** \ **Category:** Factual Questions\ **Created:** [August 29, 2018, 9:24pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492 "2018-08-29T21:24:23Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [August 30, 2018, 7:44pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/21 "2018-08-30T19:44:56Z")
> [@Lemur866](#): > > Except there is causation. When I’m at an intersection and see a red light, I stop my car. The red light caused me to decide to stop. When I see a green light, I start driving again. The green light caused me to do decide to drive again. I agree there is causation. But the alien doesn’t have enough evidence to conclude that there is causation. To the alien, it’s just “cars generally go when lights are green and stop when they are red, I wonder why?”. Any conclusions beyond that are unwarranted and merely based on speculation. ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [August 30, 2018, 8:54pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/22 "2018-08-30T20:54:26Z")
I would call it a hasty generalization. Green lights are not necessary for cars to go (for example, you could be at an intersection controlled by a stop sign, or traffic going in your direction is not controlled at all, or people could run a red light, or make a free turn on red, or move through the intersection against the red light when directed to by traffic police, and so on). Green lights are also not sufficient to go (you might have a green light but not move through the intersection to avoid causing an accident, or because you’re not paying attention, or because traffic police have indicated for you to stop, and so forth). So concluding that “green lights cause cars to go” is wrong, because it’s an overly broad generalization. What the alien can fairly conclude is that “green lights often cause cars to go, but cars with green lights don’t go, and often cars go without a green light.” This should prompt the alien to wonder if there’s a separate factor beyond green lights which better explains why cars move when they do. It might conclude – and should! – that what _actually_ causes cars to go is this separate factor which has, by definition, more explanatory power. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [August 30, 2018, 9:07pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/23 "2018-08-30T21:07:09Z")
Am I the first person to mention _Post Hoc, Ergo Propter Hoc_ (Latin: “After this, therefore because of this”)? > [@Grrr](#): > > I mean, it’s true in a sense that green lights make the cars go, but it’s actually the people _inside_ the cars that make the cars go. I thought it was the _engines_ that made the cars go. The green light causes the person to step on the accelerator. Stepping on the accelerator causes the car to go. 🙂 ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [August 30, 2018, 9:37pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/24 "2018-08-30T21:37:06Z")
> [@Thudlow\_Boink](#): > > The green light causes the person to step on the accelerator. Stepping on the accelerator causes the car to go. 🙂 Yeah, I’m not going down that rabbit hole mister! 🙂 ---
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [August 31, 2018, 1:31pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/25 "2018-08-31T13:31:00Z")
> [@g8rguy](#): > > I would call it a hasty generalization. Green lights are not necessary for cars to go (for example, you could be at an intersection controlled by a stop sign, or traffic going in your direction is not controlled at all, or people could run a red light, or make a free turn on red, or move through the intersection against the red light when directed to by traffic police, and so on). Green lights are also not sufficient to go (you might have a green light but not move through the intersection to avoid causing an accident, or because you’re not paying attention, or because traffic police have indicated for you to stop, and so forth). So concluding that “green lights cause cars to go” is wrong, because it’s an overly broad generalization. > > What the alien can fairly conclude is that “green lights often cause cars to go, but cars with green lights don’t go, and often cars go without a green light.” This should prompt the alien to wonder if there’s a separate factor beyond green lights which better explains why cars move when they do. It might conclude – and should! – that what _actually_ causes cars to go is this separate factor which has, by definition, more explanatory power. You could say all the same things about cigarettes and lung cancer. After all, some people smoke for seventy years and never get cancer, and some people get lung cancer and never smoke at all. Nevertheless, cigarettes do cause cancer. And green lights do cause cars to go. ---
**Author:** ![Flyer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/flyer/32/7298_2.png) [@Flyer](https://boards.straightdope.com/u/Flyer)\ **Post date:** [August 31, 2018, 3:13pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/26 "2018-08-31T15:13:42Z")
> [@Lemur866](#): > > Except there is causation. When I’m at an intersection and see a red light, I stop my car. The red light caused me to decide to stop. When I see a green light, I start driving again. The green light caused me to do decide to drive again. You’re still driving even when you’re not moving. Decision-making, including the decisions of when to move and when not to, is an inherent part of driving. If you don’t believe me, try drinking a lot of alcohol, and then persuade the policeman that you shouldn’t get a ticket for DUI, just because the car wasn’t actually moving. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [August 31, 2018, 4:56pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/27 "2018-08-31T16:56:23Z")
> [@Thudlow\_Boink](#): > > I thought it was the _engines_ that made the cars go. My car is sitting out in my driveway right now. It has an engine in it yet it’s not going anywhere. So an engine is another necessary but not sufficient factor in a car moving. > [@Thudlow\_Boink](#): > > The green light causes the person to step on the accelerator. Stepping on the accelerator causes the car to go. 🙂 A green light causes a person to step on the accelerator? I’ve often encountered situations where the light turns green and I see a person not step on the accelerator. (In a few cases, I’ve been that person.) There are also cases where people step on accelerators when the light is yellow or red. In many cases, people step on accelerators when there is no traffic light in the vicinity. So while there is a correlation between a traffic light turning green and people stepping on the accelerator, it clearly is not an absolute one. If an alien was to observe all of the events which occur in the vicinity of cars beginning to move, that alien would observe that the strongest correlation is between the actions of the person in the driver’s seat and the car moving. ---
**Author:** ![SpoilerVirgin](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SpoilerVirgin](https://boards.straightdope.com/u/SpoilerVirgin)\ **Post date:** [August 31, 2018, 6:46pm UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/28 "2018-08-31T18:46:21Z")
I just read an [xkcd](https://www.xkcd.com/552/) that belongs in this thread. ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [September 1, 2018, 1:28am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/29 "2018-09-01T01:28:33Z")
> [@DrCube](#): > > You could say all the same things about cigarettes and lung cancer. After all, some people smoke for seventy years and never get cancer, and some people get lung cancer and never smoke at all. Nevertheless, cigarettes do cause cancer. And green lights do cause cars to go. No. Cigarettes _can_ cause cancer, just as green lights _can_ cause cars to go. But “can” is not “do.” You would have me believe that an explanation is right even though it is sometimes wrong. I disagree. An explanation that is sometimes right may be partially correct, but it is not completely correct unless it is never wrong. Given two explanations, the one which better matches observation is to be preferred, even if the less powerful explanation is sometimes or even frequently correct, which is why we no longer adhere to geocentric models of the solar system. This is as true of traffic lights and medicine as it is of astronomy. ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [September 1, 2018, 2:21am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/30 "2018-09-01T02:21:44Z")
Let me be clearer, because I think the part about the scientific method, while true, is a distraction. The essence of my objection is this: on my understanding of English, “A causes B,” “A can cause B”, “B is caused by A,” and “B can be caused by A” are all similar but not entirely identical claims. If you disagree with this understanding, then you’ll also probably also disagree with my view that evidence for “A can cause B” does not permit one to conclude “A causes B.” ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 2:29am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/31 "2018-09-01T02:29:18Z")
> [@g8rguy](#): > > No. Cigarettes _can_ cause cancer, just as green lights _can_ cause cars to go. But “can” is not “do.” You would have me believe that an explanation is right even though it is sometimes wrong. No, the fact that A does not _fully_ explain B does not imply that there is no causal relationship. That’s not what causation means. With cigarettes we have a statistical association and a well understood mechanism. Cancer usually requires about 6 key mutations, and smoking increases the mutation rate. A proven mechanism and a statistical relationship is the _definition_ of causation. You seem to be trying to draw a distinction between “causes” and “increases the statistical likelihood of”, but there is no such distinction - that’s what it _means_ to cause something. > [@g8rguy](#): > > An explanation that is sometimes right may be partially correct, but it is not completely correct unless it is never wrong. We have no complete models for anything, just models that explain less and better models that explain more. There is literally nothing for which B _always_ follows A. Even a complete model can be probabilistic, incorporating random uncertainty. In fact a completely deterministic model for the entire universe _would_ be such a probabilistic model. > [@g8rguy](#): > > Given two explanations, the one which better matches observation is to be preferred, even if the less powerful explanation is sometimes or even frequently correct, which is why we no longer adhere to geocentric models of the solar system. This is as true of traffic lights and medicine as it is of astronomy. True enough, but that has nothing to do with your attempt to define causation as an absolute relationship rather than a probabilistic one. ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [September 1, 2018, 3:01am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/32 "2018-09-01T03:01:39Z")
If we both agree to understand “to cause something” as “to increase its probability” then we agree: green lights cause traffic to move. But I don’t cede to you the right to define “to cause” as “to make more likely.” ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 3:10am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/33 "2018-09-01T03:10:53Z")
> [@g8rguy](#): > > If we both agree to understand “to cause something” as “to increase its probability” then we agree: green lights cause traffic to move. But I don’t cede to you the right to define “to cause” as “to make more likely.” If you claim that causal relationships are not probabilistic, please cite an absolute causal relationship where B _always_ follows A. ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [September 1, 2018, 3:17am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/34 "2018-09-01T03:17:10Z")
I am forced to conclude that gravity works differently where you are. What it means to cause something is a philosophical question. “To cause means to make more probable” is undeniably one theory of causation. It’s not the only one, and I don’t see why I am forced to conclude that because it’s the one you favor it must be correct. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 3:25am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/35 "2018-09-01T03:25:49Z")
> [@g8rguy](#): > > I am forced to conclude that gravity works differently where you are. > > What it means to cause something is a philosophical question. “To cause means to make more probable” is undeniably one theory of causation. It’s not the only one, and I don’t see why I am forced to conclude that because it’s the one you favor it must be correct. Gravity is a force, not a causal relationship. (And not a force that’s not fully understood, for what it’s worth.) You can easily refute my claim that causation is probabilisitic by citing some B that is _always_ caused by some A, regardless of whatever other conditions prevail. ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [September 1, 2018, 3:52am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/36 "2018-09-01T03:52:49Z")
I see I was too opaque. If an object experiences a net force, it always moves. In what sense does that net force not cause the motion? Look, you can go read up on theories of causation (I did) and you can insist that you have the right to decide which is correct. But I am no more obliged to agree with that choice than I am to disprove it. When I go to the dictionary, I do not see “cause” defined as “make more likely.” When I go to the Stanford Encyclopedia of Philosophy, I see [multiple](https://plato.stanford.edu/entries/causation-probabilistic/) [possible](https://plato.stanford.edu/entries/causation-counterfactual/) theories of causation – I’ve linked you two – among which is one where “to cause” does loosely mean “to make more likely” and another where “to cause” does not mean “to make more likely.” But here, you claim, there’s no need to worry because you’ve got it all figured out. I hope you’ll pardon my skepticism. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 4:07am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/37 "2018-09-01T04:07:16Z")
> [@g8rguy](#): > > But here, you claim, there’s no need to worry because you’ve got it all figured out. I hope you’ll pardon my skepticism. Actually, this conversation started when _you_ were the one who claimed you had everything figured out, by _excluding_ probabilistic relationships from the definition of causation. If you want to go to canonical definitions, here’s the first two sentences of the Wikipedia article on causation: > [@](#): > > Causality (also referred to as causation, or cause and effect) is what connects one process (the cause) with another process or state (the effect), where the first is **partly** responsible for the second, and the second is **partly** dependent on the first. **In general, a process has many causes** , which are said to be causal factors for it, and all lie in its past. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 4:11am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/38 "2018-09-01T04:11:50Z")
> [@g8rguy](#): > > If an object experiences a net force, it always moves. This is not a counterexample. It’s similar to just saying: _if you account for all the different causal factors_, the effect is fully explained. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 4:22am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/39 "2018-09-01T04:22:41Z")
> [@g8rguy](#): > > When I go to the dictionary, I do not see “cause” defined as “make more likely.” ETA: So you’d argue that the hundred million or so google hits on “smoking causes cancer” are all erroneous uses of the English word “cause”? ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 1, 2018, 4:49am UTC](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492/40 "2018-09-01T04:49:52Z")
There clearly _are_ “single-cause” counterexamples that you can come up with that it would be churlish to challenge, such as: standing 10 feet from a detonating nuclear bomb causes your heart to stop beating. But the fact is: (1) Virtually all practical situations that are remotely interesting and non-trivial have multiple causes, some of which are not fully understood. We don’t require a perfect model to assert that A causes B, and it does not necessarily mean that B _always_ follows A. (2) Ultimately all abstract physical laws are probabilistic, because they must account for the randomness inherent in QM. So no ultimate physical theory will ever be framed in the form “B _always_ follows A”. (3) Common English usage clearly includes probabilistic relationships in the definition of the word “cause”. So, whether we’re talking about the underlying philosophical concept of causation, or common English semantics, it’s simply wrong to say that probabilistic relationships are excluded, in fact they form the bulk of the concept. It’s perfectly accurate to say that smoking causes cancer. [Previous page](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492.md?page=1) [Next page](https://boards.straightdope.com/t/what-types-of-evidence-is-this/820492.md?page=3)