A recent study shows that people living on the continent of North America suffer 9 times more chronic¹ fatigue² and 31 times more chronic depression than do people living on the continent of Asia. Interestingly, Asians, on average, eat 20 grams of soy per day, whereas North Americans eat virtually none. It turns out that soy contains phytochemicals called isoflavones, which have been found to possess disease-preventing properties. Thus, North Americans should consider eating soy on a regular basis as a way of preventing fatigue and depression.

In this argument, the arguer cites a study showing that North Americans suffer from an amazingly higher rate of chronic fatigue and chronic depression than people living in Asia. From an unknown source, the arguer states that Asians eat much more soy than North Americans, who eat almost none, and that soy contains disease-preventing properties. The arguer then concludes his or her argument by stating that North Americans should consider regularly eating soy as a means of battling fatigue and depression. This argument suffers from at least four critical fallacies.

For the sake of this argument, we will assume that the studies and the statistics about North Americans' and Asians' soy eating habits are correct, and that isoflavones have been found to have disease-fighting properties. Given that, there is still a problem with the arguer directly correlating the eating of soy with the prevention of disease and depression. First of all, simply because soy may have disease-preventing properties, that does not mean that it can therefore fight chronic fatigue and chronic depression. Fatigue and depression may not actually even be considered as "diseases", therefore even given the fact that soy has disease-fighting properties, it would have no effect on the "nondiseases" of fatigue and depression. Secondly³, even assuming that fatigue and depression are diseases, they are not specifically mentioned as diseases that soy or isoflavones are able to prevent. Perhaps soy can help prevent osteoporosis (bone loss), mumps⁴ or even chicken pox, but that does not mean that it can specifically address the problems of chronic fatigue and chronic depression. These two critical weaknesses alone make the argument unconvincing.

Furthermore, the arguer's conclusion is based on the idea that diet alone can prevent fatigue and depression by comparing the diets of North Americans and Asians. It is highly unlikely that diet alone is responsible for the tremendous difference in the rates of fatigue and depression between the two populations. Other factors such as lifestyles, occupations, residence in city or rural areas and levels of stress may play a much bigger factor than diet. Additionally, the arguer states that soy contains phytochemicals called isoflavones, which supposedly have disease-preventing properties. What is not stated, however, is whether these isoflavones are contained in a form in soy that is usable by the human body. It is possible that the particular configuration⁵ of the phytochemicals found in soy products is not usable by the human body, thereby⁶ producing no beneficial effects by people eating more soy products. In and of themselves, isoflavones may prevent certain diseases, but perhaps those found in soy are of no benefit to humans. By failing to address these possibilities, the arguer has presented an unconvincing argument.

In summary, the argument fails due to four major flaws in logic⁷. First, "disease-preventing" properties does not mean "fatigue and depression" preventing properties. Secondly, fatigue and depression may not even be considered as diseases. Thirdly, the arguer ignores the probability that diet alone is not the sole reason behind the increased rates of fatigue and depression for North Americans as opposed to Asians. Finally, isoflavones as found in soy may not produce the same beneficial effects as when it is found in other forms. To strengthen the argument and conclusion, the arguer should present evidence that directly links diet to fatigue and depression as well as evidence that shows that soy can specifically prevent chronic fatigue and chronic depression in North Americans.

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一项最近的研究表明，居住在北美大陆上的人们要比居住在亚洲大陆上的人们患慢性疲倦和慢性忧郁症的比例分别超出9倍和31倍。有意思的是，亚洲人平均每天只吃20克的大豆，而北美洲人却几乎一点都不吃。研究表明，大豆含有被称为异黄酮的植物化学物，这些植物化学物经科学家研究，发现拥有防病特性。因此，北美洲人应该考虑经常性地吃大豆，以此作为一种防止疲劳和压抑的方法。　

[范文正文]

在本段论述中，论述者援引了一项研究来证明，北美洲人患慢性疲倦和慢性忧郁症的比例要比居住在亚洲的人令人惊讶地高。从一项来源不明的资料中，作者陈述道，亚洲人所吃的大豆要远多于北美人，而北美人则几乎一点都不吃，而大豆却含有防病的特性。论述者在其论述的结束处陈述首，北美人应考虑经常性地吃些大豆，以此作为一种抗疲劳和抗忧郁的方法。本段论述至少犯下了四个关键性的逻辑谬误。

为了论述的缘故，我们假定关于北美人和亚洲人吃大豆的习惯这方面的研究和数据是完全正确的，并且异黄酮确实被科学家发现具有防病功效。即使在承认这些条件的情况下，论述者将食用大豆与防止疾病和抵抗忧郁直接联系起来，这一做法本身仍存在着问题。首先，即使大豆有可能具备防病特性，但这并非意味着它因此就能抵抗慢性疲倦和慢性忧郁症。疲倦和忧郁实际上甚至还不可能被视作"疾病"，因此，尽管大豆具有防病作用属实，但它对于疲倦和忧郁这些"非疾病"可能毫无作用。其次，即使我们假定疲倦和忧郁可被视为疾病，但它们没有被具体提到是属于大豆或异黄酮所能预防的那类病症。或许，大豆可以预防骨质疏松症，流行性腮腺炎或甚至是水痘，但这并非意味着它能具体地治疗慢性疲倦和慢性忧郁症这样一些问题。这二个关键性的弱点本身就足以使得该论述缺乏可信度。

进而言之，论述者的结论所依据的是这样一个理念，即通过比较北美人和亚洲人的饮食，饮食本身可以来防止疲倦和忧郁。但很难想象饮食本身造成了两类人口之间患上疲倦和忧郁症比例方面的巨大差异。其他诸多因素，如生活方式，职业，居住在都市还是乡村，以及压力程度所产生的影响可能要比饮食大得多。此外，论述者陈述道，大豆含有一种可被称为异黄酮的植物化学物，据称具有防病功效。但论述者没有作出陈述，即这些异黄酮是否是以一种被人体使用的方式被包含在大豆中。有可能是，大豆产品中所发现的植物化学物，其特定的结构并不能为人体所利用，从而对食用较多大豆产品的人并不能产生任何益处。就其本身而言，异黄酮或许可能预防某些疾病，但大豆中所发现的异黄酮对人类毫无益处，这也是有可能的。由于没有探究这些可能性，论述者所摆出的这段论述便失去了说服力。

总的说来，本段论述因为四大逻辑缺陷而难以站得住脚。首先，"防病"特性并不能等同于"疲倦和忧郁症"预防特性。其次，疲倦和忧郁甚至还不能被视为疾病。第三，论述者忽视了这样一种可能性，即饮食本身并不是造成北美人相对于亚洲人疲倦与忧郁症比例上升的唯一原因。最后，大豆中所被发现的异黄酮可能并不能产生与在其他形式中所发现的异黄酮相同的益处。若要增强其论点和结论的力度，论述者应该拿出证据，将饮食与疲倦及忧郁直接联系起来，且提供证据来证明大豆能具体地防止北美人的慢性疲倦和慢性忧郁症。