Uncertainty spreads through our lives so thoroughly that it dominates our language. Our everyday speech is made up in large part of words like probably, many, soon, great, little. What do these words mean? "Atomic war," declared a recent editorial in the London Times, "is likely to destroy forever the nation that wages it." How exactly are we to understand the word likely? Lacking any standard for estimating the probability, we are left with the judgment of the editorial writer.

Such verbal imprecision is not necessarily to be criticised. Indeed, it has a value just because it allows us to express judgments when a precise quantitative statement is out of the question.

The language of uncertainty has three main categories: (1) words such as probably, possibly, surely, which denote a single subjective probability and are potentially quantifiable; (2) words like many, often, soon, which are also quantifiable but denote not so much a condition of uncertainty as a quantity imprecisely known; (3) words like fat, rich, drunk, which can not be reduced to any accepted number because they are given different values by different people.

We have been trying to pin down by experiments what people mean by these expressions in specific contexts, and how the meanings change with age. For instance, a subject is told "There are many trees in the park" and is asked to say what number the word many mean to him. Or a child is invited to take "some" sweets from a bowl and we then count how many he has taken. We compare the number he takes when he is alone with the number when one or more other children are present and are to take some sweets after him, or with the number he takes when told to give "some" sweets to another child.

First, we find that the number depends, of course, on the items involved. To most people some friends means about five, while some trees means about twenty. However, unrelated areas sometimes show parallel values. For instance, the language of probability seems to mean about the same thing in predictions about the weather and about politics: the expression is certain to (rain, or be elected) signifies to the average person about a 70 per cent chance; is likely to, about a 60 per cent chance; probably will, about 55 per cent.

Secondly, the size of the population of items influences the value assigned to an expression. Thus, if we tell a subject to take "a few" or "a lot of" glass balls from a box, he will take more if the box contains a large number of glass balls than if it has a small number. But not proportionately more: if we increase the number of glass balls eight times, the subject takes only half as large a percentage of the total.

Thirdly, there is a marked change with age. Among children between six and fourteen years old, the older the child, the fewer glass balls he will take. But the difference between a lot and a few widens with age. This age effect is so consistent that it might be used as a test of intelligence.

模糊现象已经无孔不入地扩展到我们生活的各个方面，以致模糊现象也扩展到了我们的语言当中。我们的日常讲话很大一部分是由"也许"、" 好多"、"不久"、"大量"、"很少"这类词汇所构成的。这些词汇意味着什么？英国伦敦《泰晤士报》在最近的一篇社论中说"原子战争很可能会永久性地毁灭了进行原子战的国家"。我们怎样才能确切地理解"很可能"这个词汇？因为要估计某事的可能性，没有什么标准可依据，我们只能由着社论的作者去估计判断了。

对这种用词不够精确的模糊语言，倒不一定要加以批评责备。其实，这种模糊语言有它一定的使用价值，因为当我们不能用精确的数量来叙述时，这种模糊语言使我们能表达出对各种事物的判断。

模糊语言有三大类：（1）"很可能"、"有可能"、"肯定会"、之类的词。这类词表示个人主观认为的可能性，这些词在发言人的心目中是有一定的潜在的数量的；（2）"很多"、"经常"、"很快"之类的词表示的是模糊的状况倒不如说表达的是知道得不够确切的数量；（3）"肥胖"、"富有"、"酒醉"之类的词，这类词不能精确到大家都能同意接受的数字。；在这来，因为不同的人对这些词都会有不同的评价。

我们一直都想通过多次实验来解释在特定的语言环境当中，人们使用这些词语都用于哪些意思，解释明白随着年龄的不同在使用这些词语时意义上有了哪些变化。例如，我们告诉一位被测试者"公园里有很多树"。然后再问这位被测试者，"很多"这个词在他看来意味着多少。或者我们请一个小孩从一只碗里拿取"一些"糖块，然后我们数一数他拿取了多少块糖。我们把只有他一人在场时所拿取的糖块，跟还有一个或一些儿童在场时，这些儿童在他拿了糖之后也要去拿糖块，他所拿取的数量比较一下；或者把只有他一个人在场时他所取的糖块数量跟你告诉他还要分给另一儿童"一些"糖块时，他所拿取的数量比较一下。

首先，我们发现孩子所拿取的糖块数量，当然要取决于碗里有多少块糖的数量。对大多数人来说"有些朋友"指的是5个左右，而"有些树木"则指的是20棵左右。但是，在互相没有什么关连的事物范畴之内有时却能表示出平行的数值概念。例如，可能性这类话在天气预报和政治预测当中的意思是相同的；在"确实有可能会"这类话中，对一般人来说，这表示约有70%的可能性；若说"很可能会"就意味着约有60%的可能性；若是说"有可能会"这就意味着55%的可能性了。

第二，测试所用物品数量的多少会影响某一词语或某一说法所代表的实际数值。因此，如果我们让某一位被测试者从一个盒子中拿取"很少"或"很多个"玻璃球。如果盒子里的玻璃球少，他就拿取得少。但取多少并不是按比例增多的：如果我们把玻璃球的总数增加到8倍，被测试者也只从玻璃球的总数量的某个百分数中取走一半。

第三，随着年龄的增长拿取多少个也有明显的变化。在6到14岁的孩子们中间，年纪越大的孩子，他所拿取的玻璃球就越少。但是拿取"很多个"和拿取"很少"之间的差距随着年龄的增长而加大了。这种年龄的差别是十分稳定的，可以把它用作智力测验。