GMAT邏輯assumption解題思路：構(gòu)建橋梁

GMAT邏輯中的assumption要求考生找出一個(gè)選項(xiàng)來當(dāng)做題面上的推理或計(jì)劃的前提，只有當(dāng)該前提存在時(shí)該推理才成立或者該計(jì)劃才能達(dá)到目的。換句話說，在做出該推理或計(jì)劃時(shí)已經(jīng)默認(rèn)了某個(gè)前提的存在，否則該推理或計(jì)劃是不行的、沒道理的，只是題面上沒有明說而已。

如： 我多想把你留在身邊啊，但城市里不能養(yǎng)狗。所以，我只能放棄你了。

這句話中的前提可以認(rèn)為是“城市里不能養(yǎng)狗”，結(jié)論是“我只能放棄你了”。乍看我們不覺得有什么問題，因?yàn)槠綍r(shí)生活中我們都在這么說。但從推理的角度去理解，憑什么“城市里不能養(yǎng)狗”就能得出“我只能放棄你了”？除非——除非這個(gè)“你”就是一條狗，而且“我”養(yǎng)這條狗就養(yǎng)在城市里；如果“你”不是條狗，或者“我”養(yǎng)狗不是養(yǎng)在城市，那么這個(gè)推理就不成立了。

因此這里我們就找到了這個(gè)推理的兩個(gè)assumption——“你”是一條狗，且“我”養(yǎng)這條狗養(yǎng)在城市。這里我們就得出了assumption的第一個(gè)解題方向：構(gòu)建橋梁。

什么時(shí)候需要“構(gòu)建橋梁”？如果你發(fā)現(xiàn)結(jié)論里比較突兀地出現(xiàn)了一個(gè)前提中并沒有提到過的概念，那你可能就需要構(gòu)建橋梁來把這個(gè)結(jié)論中的概念與前提中的東西聯(lián)系起來。否則憑什么結(jié)論中可以如此任性地提到不想關(guān)的東西？

例1：
　　Even though most universities retain the royalties from faculty members’ inventions, the faculty members retain the royalties from books and articles they write. Therefore, faculty members should retain the royalties from the educational computer software they develop.
　　The conclusion above would be more reasonably drawn if which of the following were inserted into the argument as an additional premise?

A. Royalties from inventions are higher than royalties from educational software programs.
　　B. Faculty members are more likely to produce educational software programs than inventions.
　　C. Inventions bring more prestige to universities than do books and articles.
　　D. In the experience of most universities, educational software programs are more marketable that are books and articles.
　　E. In terms of the criteria used to award royalties, educational software programs are more nearly comparable to books and articles than to inventions.

這個(gè)題目還比較短，不過很多學(xué)生會(huì)對(duì)royalty一詞產(chǎn)生疑慮，明顯不是我們平時(shí)講的“皇室”的意思。但這對(duì)我們做題并不產(chǎn)生多大的影響，把它當(dāng)做一個(gè)東西即可。閱讀完題面，我們大致能知道在講什么：盡管學(xué)校能retain 來自invention的royalty，但教職員工能retain來自books and articles的royalty。

因此，教職員工能retain來自educational computer software的royalty。
　　這里，結(jié)論中提到了的educational computer software在前提中一點(diǎn)都未提及，屬于空降兵，因此我們必須得構(gòu)建橋梁，把它和前面講的東西聯(lián)系起來。對(duì)語義稍作分析，我們明顯發(fā)現(xiàn)，在“royalty由誰來retain”這件事情上，educational computer software更接近于books and articles，而不像是inventions。最終答案選E。

例2：

The technological conservatism of bicycle manufacturers is a reflection of the kinds of demand they are trying to meet. The only cyclists seriously interested in innovation and willing to pay for it are bicycle racers. Therefore, innovation in bicycle technology is limited by what authorities will accept as standard for purposes of competition in bicycle races.

Which of the following is an assumption made in drawing the conclusion above?

A. The market for cheap, traditional bicycles cannot expand unless the market for high-performance competition bicycles expands.
　　B. High-performance bicycles are likely to be improved more as a result of technological innovations developed in small workshops than as a result of technological innovations developed in major manufacturing concerns.
　　C. Bicycle racers do not generate a strong demand for innovations that fall outside what is officially recognized as standard for purposes of competition.
　　D. The technological conservatism of bicycle manufacturers results primarily from their desire to manufacture a product that can be sold without being altered to suit different national markets.
　　E. The authorities who set standards for high-performance bicycle racing do not keep informed about innovative bicycle design.

題面推理如下：對(duì)innovation感興趣同時(shí)也愿意買單的只有bicycle racers，因此，innovation受到authorities建立的competition standard的限制。

這里，結(jié)論中的authorities和competition standard就是前提中沒有提到的東西。前提說innovation受bicycle racers的影響，結(jié)論卻說innovation受authorities和他們的competition standard的影響，這當(dāng)然非常突兀。

相當(dāng)于在說，“我聽爸爸的，所以我聽媽媽的”。這個(gè)推理的成立必須基于一個(gè)前提——“爸爸聽媽媽的”。整體是，“我聽爸爸的，而爸爸聽媽媽的，所以我聽媽媽的”。因此這個(gè)題目最終的答案應(yīng)該是說bicycle racers聽authorities和他們的competition standard，選C。

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