本論文主要在描述西班牙文、英文與中文「雙重否定」在句法上的表現。我們試著探討在什麼情況下「雙重否定」會等於肯定或者是否定，還是造成語意上的不清不楚。 語言中「雙重否定」的現象並不總是遵循著理則學上「負負得正」的規則，往往兩個否定的字在同一個句子裡出現時，仍會產生否定的意味，比如說：西班牙文No tengo ningun libro（我一本書也沒有）這句話裡有no跟ningun兩個否定的字眼，整句話的意思仍然是否定的。Otto Jespersen（1917）指出：從心裡的層面來看，「雙重否定」可視為「多餘」的現象，其目的在減輕聽話者的心理負擔，同時也暗示著說話的不確定。不過，雙重否定等於肯定的情形不是沒有，像是No voy a salir sin paraguas（沒有雨傘我不出門）這句話的意思其實就是「有雨傘我才出門」。此外，雙重否定也會造成訊息焦點的模糊，例如：Él no está descontento（他不是不高興），其高興的程度可能只有他自己知道。

The present paper is a contrastive study of double negation among the Spanish, English, and Chinese languages. In natural language, the simplest form of negation is verb phrase negation rather than sentence negation. Negation is almost always applied primarily to some part of a statement, though this often has the effect of negating the statement as a whole. When logicians insist that ‘two negatives make an affirmative’, their assumption is not proved by actual usage in most languages. For example, in Spanish a sentence like No tengo ningún libro includes two negative words ‘no’ and ‘ningún’, but the whole sentence is still negative. Otto Jespersen (1917: 62) says that “the psychological reason being that the detour through the two mutually destroying negatives weakens the mental energy of the hearer and implies on the part of the speaker a certain hesitation……” On the other hand, it is also possible that two negative words appearing in the same sentence can make an affirmation. For example, a sentence like No voy a salir sin paraguas (I will not go out without an umbrella) means Voy a salir con paraguas (I will go out with an umbrella) or Si no tengo paraguas, no voy a salir (If I have no umbrella, I won´t go out). Finally, two negations sometimes add confusion to the information. For example, Él no está descontento (He is not unhappy). This sentence does not tell how unhappy he is nor means he is happy. We know that it is probably impossible to write a concluding study on a contentious and evolving subject like this one, but we think that this paper can provide readers a clear idea about the syntactic differences between the mentioned three languages.