就其本身而言，这一原则是完全简单的——只需一行字就可以表述出来，而且很容易理解。“人类有理由单独或集体地干涉其成员的行动自由的唯一目的是自我保护”(密尔，1869:pg 9)。后面的几行丝毫没有与这句话相抵触，它们只是强调。然而，这个原则本身是简单的，并不意味着它的含义和分支是如此简单;这似乎很清楚，但逻辑上的荒谬是可以找到的- -例如，当人类成员不知道他的活动有多危险时，家长式的干涉能被证明是正当的吗?最典型的例子就是这座桥，它看起来完好无损，但如果有人踩上去，它就会倒塌。对密尔原则的直接和字面的解读，将禁止任何人在一个人不知不觉地跨上这座桥的时候干涉——然而，这种解读对密尔或不幸无知的社会成员都是不公平的。因此，这个原则表述起来很简单，但理解起来却不那么简单。它有其微妙之处，必须加以考虑，而不是直接地接受。
In and of itself, the principle is entirely simple – it takes barely a line to be stated, and is easily understood. “The sole end for which mankind are warranted, individually or collectively, in interfering with the liberty of action of any of their number, is self-protection” (Mill,1869: pg 9). He goes on to explain exactly what he means, but that single line encapsulates the principle itself, without requiring additional clarification. Subsequent lines do not in any way contradict this statement, they merely emphasise. The principle by itself being simple, however, does not mean that its implications and ramifications are so straightforward; it may seem clear, but logical absurdities can be found – can paternalistic interference be justified when, for example, the member of mankind has no knowledge of how dangerous his activities are? The classic example is that of the bridge, which appears to be intact, but will collapse if a man steps on it. A direct and literal reading of Mill’s principle would forbid anyone from interfering when a man unknowingly took a step onto this bridge – such an interpretation would not, however, be fair either to Mill or to the unfortunately ill-informed member of society. The principle is therefore simple to state, but not so simple to understand. It has its subtleties, and must be considered, rather than straightforwardly accepted.