However, then there is a whole other class of things, which are not so easy to control.

然而，还有另外一类事情，不那么容易控制。

But the relationship between classes of things is not always so obvious.

索菲。 但是事物类之间的关系并不总是那么明显。

Plato even used to object to this class of things as being a geometrical fiction.

柏拉图甚至过去反对这类事物是几何虚构的。

And the same applies to our knowledge of other people's minds, or of any other class of things of which no instance is known to us by acquaintance.

这同样适用于我们对其他人的思想的了解，或对我们所不了解的任何其他类别事物的了解。