1 00:00:00,012 --> 00:00:04,180 . >> Remember, in unit four, one of the ways 2 00:00:04,180 --> 00:00:10,228 that we discussed to refute an argument is to show that it's invalid by using 3 00:00:10,228 --> 00:00:15,563 parallel reasoning. And, I want to give an illustration right 4 00:00:15,563 --> 00:00:21,837 now of how an argument can be refuted by means of parallel reasoning. 5 00:00:21,838 --> 00:00:27,938 And the target of my refutation is going to be the fascinating argument, gay sex 6 00:00:27,938 --> 00:00:32,981 human nature and benefits, submitted by Matthew Ivan Bennett. 7 00:00:32,981 --> 00:00:38,567 And I should insist, before going on to refute this argument by parallel 8 00:00:38,567 --> 00:00:44,519 reasoning, that the conclusion of Bennett's argument may very well, for all 9 00:00:44,519 --> 00:00:49,112 I say here, be true. My only point, is that whether or not the 10 00:00:49,112 --> 00:00:53,303 conclusion is true, the argument itself is not valid. 11 00:00:53,303 --> 00:00:56,660 And let me illustrate that point right now. 12 00:00:56,660 --> 00:01:02,737 Here's how the argument goes. Premise one, the simplest definition of 13 00:01:02,737 --> 00:01:06,603 nature is the universe with all of its phenomena. 14 00:01:06,603 --> 00:01:12,979 Premise two, the simplest definition of human nature is, therefore, the phenomena 15 00:01:12,979 --> 00:01:17,996 of being human. Premise three, a phenomenon of being human 16 00:01:17,996 --> 00:01:24,860 is seeking the satisfaction of mutually beneficial goals through sex, such as 17 00:01:24,860 --> 00:01:30,463 comfort and bonding. Premise four, not all sex is reproductive. 18 00:01:30,463 --> 00:01:37,370 Premise five, so human nature allows non-reproductive purposeful beneficial 19 00:01:37,370 --> 00:01:41,057 sex. Premise six, gay sex, although it is non 20 00:01:41,057 --> 00:01:47,864 reproductive, can often benefit those who practice it through comfort and bonding. 21 00:01:47,864 --> 00:01:53,915 Conclusion, therefore, gay sex is often beneficial in a way that accords with 22 00:01:53,915 --> 00:01:57,751 human nature. Okay, that's Benton's argument. 23 00:01:57,751 --> 00:02:03,518 And as I said, the conclusion of that argument may very well be true. 24 00:02:03,518 --> 00:02:09,591 But now, let me try to refute that argument by dint of parallel reasoning. 25 00:02:09,591 --> 00:02:16,744 So consider the following argument. One phenomenon of being human is seeking 26 00:02:16,744 --> 00:02:25,456 easy, and affordable sources of nutriment, finding nutrition in ways that are not too 27 00:02:25,456 --> 00:02:33,266 expensive to obtain or consume. Premise two, not all nutrition is farmed. 28 00:02:33,266 --> 00:02:37,222 Right? There's plenty of nutrition that we get 29 00:02:37,222 --> 00:02:42,084 that's not farmed. Eating berries off of the bush, eating 30 00:02:42,084 --> 00:02:48,692 animals that we've hunted in the wild. Premise three, so human nature allows for 31 00:02:48,692 --> 00:02:54,421 the consumption of non-farmed, wild, easily obtainable nutriment. 32 00:02:54,421 --> 00:03:03,397 Premise four, eating senile people, though they're not farmed, is a way of obtaining 33 00:03:03,397 --> 00:03:11,272 nutrient that's very easy, that's very affordable, and in fact, avoids the 34 00:03:11,272 --> 00:03:17,756 draining on social resources that is created by senescence. 35 00:03:17,756 --> 00:03:27,894 Conclusion, eating senile people often accords with human nature in a way that's 36 00:03:27,894 --> 00:03:33,841 beneficial. Now, I hope none of you are convinced by 37 00:03:33,841 --> 00:03:39,327 my second argument. Although it's true that all the premises 38 00:03:39,327 --> 00:03:45,217 of the second argument are correct, I don't believe that the conclusion is 39 00:03:45,217 --> 00:03:49,262 correct. I'm quite certain that the conclusion is 40 00:03:49,262 --> 00:03:53,494 not correct. If human nature means anything, if human 41 00:03:53,494 --> 00:03:58,785 nature rules out anything, then it rules out eating senile people. 42 00:03:58,785 --> 00:04:05,021 But, if the conclusion of that argument is not correct, even though the premises are 43 00:04:05,021 --> 00:04:10,806 correct, what that shows is that the second argument, the argument that I just 44 00:04:10,806 --> 00:04:16,187 constructed, is not valid. Its premises might all be true, but it's 45 00:04:16,187 --> 00:04:20,699 conclusion is false. And so the argument can't be valid. 46 00:04:20,699 --> 00:04:24,557 Now, let's go back to Matthew Benton's argument. 47 00:04:24,557 --> 00:04:30,501 Benton's premises might all be true. And his conclusion might also be true. 48 00:04:30,501 --> 00:04:34,957 But even if his premises and his conclusion are true, that doesn't show 49 00:04:34,957 --> 00:04:38,844 that the argument is valid. Of course, you can have an invalid 50 00:04:38,844 --> 00:04:42,206 argument whose premises and conclusion are all true. 51 00:04:42,206 --> 00:04:46,637 And what I've attempted to do by constructing a parallel argument is to 52 00:04:46,637 --> 00:04:51,887 show that whatever the truth of Benton's premises and his conclusion, the argument 53 00:04:51,887 --> 00:04:56,477 that he's built is not valid. It follows the same rule as the argument 54 00:04:56,477 --> 00:05:00,202 that I constructed. Well, if it follows the same rule, then 55 00:05:00,202 --> 00:05:04,366 the two arguments are both either valid or they're both not valid. 56 00:05:04,366 --> 00:05:09,388 Since my argument is clearly not valid, I conclude that his argument must not be 57 00:05:09,388 --> 00:05:13,996 valid either, whether or not its premises and its conclusion are true. 58 00:05:13,996 --> 00:05:20,761 That's an example of refutation by parallel reasoning.