PLATO described love as a serious mental disease. Aristotle saw it as a single soul inhabiting two bodies. Tina Turner dismissed the feeling as a second-hand emotion. The nature of love—how and when and why and with whom humans fall for each other—has preoccupied thinkers through the ages. Now a philosopher and a scientist have a go in two new and markedly different books. 柏拉图将爱情描述为一种严重的精神疾病；亚里士多德认为爱情是一个灵魂孕育在两个躯体里；蒂娜?特纳则对爱情不屑一顾，视之为二手的情感。古往今来，所有思想家都在思索爱情的本质：人们如何相爱？何时坠入爱河？为何相爱？与谁相爱？如今，一名哲学家和一名科学家各自发表了一本显著不同的新书，试图回答这一难题。

　　In his latest work, "In Praise of Love", Alain Badiou, a French philosopher, identifies three prevailing philosophical views of love. It can be an ecstatic encounter; an unsentimental contract; or an illusion, best treated with scepticism. He rejects all three. For Mr Badiou, love is the decision to live life through two perspectives, that of both the lover and the beloved. As such, it is more than the sum of its parts. Love "is a construction," he writes, "a life that is being made, no longer from the perspective of One but from the perspective of Two." 法国哲学家阿兰. 巴迪乌(Alain Badiou)最近出版了新书《歌颂爱情》，他在书中提到了哲学界三个主流的爱情观。爱情可能萌生于一次心动的邂逅，也可能是一个不动情绪的契约或一种似是而非的美好幻觉。巴迪乌对这三种观点都不以为然。在他看来，爱情就意味着相爱的两人要选择从两种角度来生活：即爱与被爱的角度。所以，爱情并不只是两个人生活片段的简单拼凑。巴迪乌写道：“爱情是‘一种建构'，恋爱双方不再单从各自的角度生活，而是从双方的角度，创造出一种全新的生活方式。”

　　Mr Badiou sees risk as central to love. A loving relationship demands multiple and shared perspectives, which always give rise to incongruences and tensions. He reserves special scorn for dabblers in internet dating, who evidently believe that the search for "a photo, details of his or her tastes, date of birth, horoscope sign, etc" will ultimately net "a risk-free option". This is to neglect the very essence of love, according to Mr Badiou, which involves the presence of risk, the possibility of failure and the need for vulnerability. 巴迪乌认为爱情必然存在风险。恋爱关系的维持需要恋爱双方从多个角度看待问题，互相理解，这也常常导致冲突和争执。巴迪乌尤为鄙视通过网络寻找恋爱对象的人，这些人视爱情如儿戏。显然，他们认为：只要搜索到“照片、喜好、年龄、星座等信息”与自己要求相符合的他或她，就能谈一场毫无风险的恋爱。巴迪乌认为，这种行为忽略了爱情的本质：爱情本就存在风险，可能失败，需要双方适时地展示自己脆弱的一面。

　　The book's chatty style (it is based on a conversation with Nicolas Truong, a French journalist) lends a deceptive simplicity to the ideas within. Get to work unpicking these concepts and it soon becomes plain that, like many French philosophers, Mr Badiou sacrifices clarity for linguistic zip and sparkle. Nonetheless, he leaves the reader with an incisive overview of philosophical thinking on love, from Plato to Kierkegaard to Lacan. 这本书语言亲切（主要内容基于与法国记者Nicolas Truong的谈话），朴实简单的文字下蕴含着深刻的思想。如若将这些概念分开来看，很快就可以发现：与很多法国哲学家一样，巴迪乌并未选择一语道破，而是玩弄起辞藻，妙语连珠，意味深长。尽管如此，他在书中对自古以来关于爱情的各种哲学思考做了犀利的总结，从柏拉图到齐克果再到拉康，一应俱全，读者可借机一窥究竟。

　　Robin Dunbar's book, "The Science of Love and Betrayal", is—perhaps surprisingly—easier to get to grips with. Dr Dunbar, a professor of evolutionary anthropology with a study in this week's science section (see article), is best known for "Dunbar's number", the limit to the number of people with whom one can maintain stable social relationships. He laments that scientists have largely ignored the concept of love. In this book he bridges the gap between the biological explanations for humans' romantic behaviour and the psychological, historical, social and evolutionary contexts that help to shape it. 相比之下，罗宾.邓巴（Robin Dunbar）的书《爱与背叛的科学》更容易理解，这一点或许出人意料。邓巴是一名进化人类学教授，他在本期杂志的科技部分也发表了一篇研究。邓巴以其提出的“邓巴人数（Dunbar's number）”最为出名。邓巴人数指能与某个人维持稳定人际关系的人数上限。他感到遗憾的是，科学家们大都忽略了爱情的含义。邓巴在书中不仅探讨了人类做出浪漫行为的生物学原因，还将这些原因与起到推波助澜作用的心理、历史、社会和进化环境等因素更为紧密地联系起来。

　　In particular, he is interested in why humans have developed such an affinity for "pairbonding", despite the fact that strictly monogamous mating and rearing systems are not terribly advantageous in evolutionary terms. Monogamy is not unique to humans. What is unique, however, is the intensity with which the species falls in love. Nearly every human culture in history exhibits this complex sense of longing, Dr Dunbar observes. 尽管严格的一夫一妻婚育制度并非十分有利于人类的进化，但人们还是喜欢有固定的配偶，邓巴对这一现象的原因尤其感兴趣。一夫一妻制并非只存在于人类社会，其它物种之间也有，但人与人相爱的深度却是其它物种不可比拟的。据邓巴观察，从古至今，几乎每个时期的人类文明都显示出了这种渴望爱情的复杂情感。

　　To understand this predisposition for monogamy, he takes readers through the myriad feelings of love, from the heady, breathless exhilaration of falling, to the stubborn persistence of familial affection, to the bitterness of betrayal. Throughout the book Dr Dunbar excels at taking obvious and familiar information—men prefer curvy women; women prefer men who dance well; older women rarely reveal their ages in lonely-hearts columns—and explaining the complex and often unexpected evolutionary science that lies behind it all. 为了弄清楚人类社会一夫一妻传统的起源，邓巴向读者阐述了恋爱过程所包含的各种错综复杂的情感：刚坠入爱河时的恋人陶醉其中，激动得无法呼吸；组成家庭后双方视彼此为亲人，不离不弃；遭到爱人背叛后，前尘往事如尘埃、内心唯有苦涩酸楚。邓巴擅于在整本书中运用显而易见的常识——男人喜欢曲线美的女人；女人喜欢舞技高超的男人；年龄稍大的女性很少会在有情人专栏透露自己的年龄——并解释这些现象背后所隐藏的复杂的进化科学，往往出人意料。

　　Love is a journey, a game, a many-splendoured thing. Though some give it a bad name (if Jon Bon Jovi is to be believed), the rest of us find the subject endlessly fascinating. The struggle to understand such a mystifying phenomenon invariably requires the help of philosophers and scientists, and others besides. Good news for Mr Badiou and Dr Dunbar. 爱情是一次旅行，一场游戏，一件充满奇妙的事。尽管有人诋毁爱情（如Jon Bon Jovi的歌曲所唱），其它人则认为它永远充满魅力。爱情如此神秘，要弄懂它，哲学家和科学家的帮助必不可少。同时还需要其它人的帮助，巴迪乌和邓巴的努力可算是没有白费。