argument47[0806G-desperado小组]第五次作业by hongdan

hongdanUID: 2228730

47.Scientists studying historical weather patterns have discovered that in the mid-sixth century, Earth suddenly became significantly cooler. Although few historical records survive from that time, some accounts found both in Asia and Europe mention a dimming of the sun and extremely cold temperatures. Either a huge volcanic eruption or a large meteorite colliding with Earth could have created a large dust cloud throughout Earth's atmosphere that would have been capable of blocking enough sunlight to lower global temperatures significantly. A large meteorite collision, however, would probably create a sudden bright flash of light, and no extant historical records of the time mention such a flash. Some surviving Asian historical records of the time, however, mention a loud boom that would be consistent with a volcanic eruption. Therefore, the cooling was probably caused by a volcanic eruption.

提纲：
1.亚洲地区记录的巨响的确是来自火山喷发，但论者没有提供任何资料证明那声巨响与火山喷发有关。另外论者也没有提供资料这声巨响是在时候发生的，是否紧跟着就气温下降了。如果巨响发生时气温已经下降，就不能说明气温下降与这巨响有关。
2.当时没有发生陨石撞地球，但这也不一定被保证成立。首先论者只是说现存资料里没有记录，但是不排除有关记录被毁坏了，或是还没有被发现。另外撞击的白光是否是全球都能看见，论者也没有提供资料，有可能白光是在当时没被记录下来。
3.它因为排除了陨石的可能性而认为是火山，但除了这两种原因之外是否就不再存在其他可能性了，论者没有告诉我们是否只有这两种情况会造成全球气温突然下降。

The arguer professes that the suddenly cooling of Earth was probably caused by a volcanic eruption. Due to the fact that no historical records of a flash related to meteorite collision and Asian historical records of a loud boom related to volcanic eruption, the argument is well presented, yet a close scrutiny reveals that it is far from satisfactory reasoned. Indeed, the argument suffers from several logical flaws, listed as follows.

The threshold problem involves in this argument is the arguer’s unfair assumption that the loud boom recorded in Asian history is attributed to a volcanic eruption. Just based on the probability that a loud boom is consistent with a volcanic eruption, the arguer takes for granted that the occurrence of the loud boom is related to a volcanic eruption and the volcanic eruption doomed to happen with the loud boom. However, it is entirely possible that other alternatives may lead to a loud boom, such as a big rock knocking on the earth, explosion of some powerful weapon, or even earthquake and so forth. Moreover, because when the loud boom happened, a volcanic eruption was not mentioned in historical recordings, it is more possible that other events had leaded to the loud boom. Without rolling out these or those alternative reasons, the loud boom might have nothing to do with a volcanic eruption, let alone will lead to the sudden decrease of the Earth temporary.

Even assuming that the loud boom had happened together with a volcanic eruption, the author still do not mention any information about when the loud boom happened and whether the earth temperature decreases as soon as the loud boom happened. If the earth temperature has decreased before the loud boom, we will arrive nothing about the relationship of loud boom and temperature decrease. Besides, if after a long time when the loud boom happened, the earth temperature decrease, the author’s conclusion is more unconvincing. In this sense, their cause-and effect relationship is unwarranted.

Another premise in the argument lies in the assertion that a large meteorite colliding with Earth did not happen. To support this assertion, the author cited the fact that no extant historical records of the time mention a bright flash of light, which always accompanied with meteorite collision. Even so, the author cannot exclude the possibility that a large meteorite collision did happen in the past. Perhaps the related recordings about the bright flash of light are ruined after a long historical time. Or perhaps the flash happened so instantly that nobody had observed at that time. In addition, whether the flash can be grasped by the whole world remains a doubt. In such case, it is very likely that only a few residents in remote areas have the opportunity to see the flash, but the scant recording techniques lead to the failure of recording the flash. Without providing abundant evidence to exclude these possibilities, the conclusion is not convincing.

Granted that the above mentioned problems can be well validated, the arguer still make an “either-or” fallacy. Are there only two reasons that will result in the decrease of earth temperature? As long as one is proved to be excluded, is the other one the only reason to explain temperature cooling? However, the argument fails to take other factors into consideration. It is common sense that nature environment is fraught with random changes and is highly influenced by humans, therefore it is extremely possible that other natural factors or some human behaviors have contributed to this phenomenon. In such case, the proposition of the author’s conclusion is too hasty.

In sum, the argument is not as convincing as it stands. To bolster the conclusion, the author should provide concrete information about the volcanic eruption, such as whether it did happen and its real impact on natural environment. In addition, the research on whether there exist other possibilities can lead to sudden cooling of earth temperature.