The motions of men must be such as suggest their dignity or their baseness.

Nature varies the seed according to the variety of the things she desires to produce in the world.

There are three classes of people: those who see, those who see when they are shown, those who do not see.

There is no result in nature without a cause; understand the cause and you will have no need of the experiment.

O neglectful Nature, wherefore art thou thus partial, becoming to some of thy children a tender and benignant mother, to others a most cruel and ruthless stepmother? I see thy children given into slavery to others without ever receiving any benefit, and in lieu of any reward for the services they have done for them they are repaid by the severest punishments.

All our knowledge hast its origins in our perceptions … In nature there is no effect without a cause … Experience never errs; it is only your judgments that err by promising themselves effects such as are not caused by your experiments … Science is the observation of things possible, whether present or past; prescience is the knowledge of things which may come to pass.

Even the richest soil, if left uncultivated will produce the rankest weeds.