Since nothing can exist that does not fulfil the conditions which render its existence possible, the different parts each being must be co-ordinated in such a way as to render possible the existence of the being as a whole, not only in itself, but also in its relations with other beings, and the analysis of these conditions often leads to general laws which are as certain as those which are derived from calculation or from experiment.

It is evident that one cannot say anything demonstrable about the problem before having resolved these preliminary questions, and yet we hardly possess the necessary information to solve some of them

The appearance of the bones of quadrupeds, especially those of complete bodies in the strata, tells us either that the layer itself which carries them was in earlier times dry land or that dry land was at least formed in the immediate area.

Since nothing can exist that does not fulfil the conditions which render its existence possible, the different parts each being must be co-ordinated in such a way as to render possible the existence of the being as a whole, not only in itself, but also in its relations with other beings, and the analysis of these conditions often leads to general laws which are as certain as those which are derived from calculation or from experiment.

Hence the same instant which killed the animals froze the country where they lived. This event was sudden, instantaneous, without any gradual development.

The observer listens to nature: the experimenter questions and forces her to reveal herself.

Moreover, it thus follows that not a great deal of time was needed for the large animals of the three major parts of the world to become known to the people who spent time on the coasts of those regions.