The Natural World

Pack of Animals by unknown

The Celtic world was very close to nature. To a Celt, outside the walls of his dun or village -- beyond the fields, the natural world was spread for hundreds of miles. The Celts saw pathways through this wilderness, but did not build any thing we would recognize as roads. These paths were few. The great forests still covered Cymru, Alba, and Eriu. And the great wetlands have not even been drained. Even the mountains were not climbed.
However, a Celt knew a lot about the natural world. They knew about the plants and animals of this natural world. Hunting was great sport to a Celt, it was a part of everyday life. After all, one of the most common magical things was that a Celt could be turned into an animal.
Unlike some other primitive cultures, a Celt did not believe in a host of monsters and chaos beings in the wilderness. Celts knew that real animals dwelt in the forests and wilderness. If there was anything supernatural, it was just that, "super" natural. The creatures of the Otherworld were not hideous monsters to be conquered, but natural creatures as natural as the cat or the lion today.
The few strange beasts that were encountered were seen as unique creatures. They were created by magic for a purpose, not a whole species. After all, if you encountered a lion or a cat that could turn itself into a ball of fire protecting treasure, then that would be seen as a unique animal. The Celts saw such creatures as wonders.

Animal Intelligence and Speech

Horses in the Wilderness by Bureau of Land Management

In the world of the Blessed Isles, animals are seen as intelligent creatures with their own motives and aims. They were eager to help or hinder humans. Animals are thought to understand speech and speak. If a white horse came up to a man and suddenly spoke to him, it was regarded as natural.