上句见：Day309
The Story of Philosophy《哲学的故事》第1章Plato第5节V. The Political Problem第6段第3句：

The more Plato thinks of it, the more astounded he is at the folly of leaving to mob caprice and gullibility the selection of political officials — not to speak of leaving it to those shady and wealth-serving strategists who pull the oligarchic wires behind the democratic stage. Plato complains that whereas in simpler matters — like shoe-making — we think only a specially-trained person will serve our purpose, in politics we presume that every one who knows how to get votes knows how to administer a city or a state. When we are ill we call for a trained physician, whose degree is a guarantee of specific preparation and technical competence — we do not ask for the handsomest physician, or the most eloquent one; well then, when the whole state is ill should we not look for the service and guidance of the wisest and the best? To devise a method of barring incompetence and knavery from public office, and of selecting and preparing the best to rule for the common good — that is the problem of political philosophy.
浙江大学译本：生病了，我们要找有行医执照的大夫，因为那是他受过正统教育和相技术培训的证明——我们不要相貌俊美或能说会道的大夫。那么，假若整个国家生了病，难道我们就不应该找寻最具智慧、最优秀的人来服务和领导吗？

解析

1、When we are ill we call for a trained physician, whose degree is a guarantee of specific preparation and technical competence — we do not ask for the handsomest physician, or the most eloquent one;
生病了，我们会去找训练有素的医生，他的证书便是受过特定培训及专业能力的证明——我们不会要求找相貌俊美或者最能说会道的医生；
physician: a medical doctor; a medical doctor who is not a surgeon医生；尤指内科医生
Never change your diet without first consulting your physician.要改变饮食习惯，一定要先向医生咨询。《健康小秘密》

2、well then, when the whole state is ill should we not look for the service and guidance of the wisest and the best?
那么， 当整个国家“生病”了，难道我们不应该找寻最有智慧的、最优秀的人的服务及指引吗？

生病了，我们会去找训练有素的医生，他的证书便是受过特定培训及专业能力的证明——我们不会要求找相貌俊美或者最能说会道的医生；那么， 当整个国家“生病”了，难道我们不应该找寻最有智慧的、最优秀的人的服务及指引吗？

这句话又用了一个类似来指出领导者的重要性。个体生病了，知道找合适的人，不是凭外在；国家生病了，医“它”更是应该万里挑一。而不是像前段中民众根据演说等外在来确定。这里也暗指了领导要像医生一样经过训练的，要有证明，不是凭外貌及口才。