Whole Earth Catalog held to two major philosophies. First, that as humans have come to master their environment, altering it at will for most any purpose, they should be responsible about how they do it and make a world that is fit for mankind, animals, plants, and the whole of nature. Second, doing that requires sharing the knowledge and tools needed to live that way. As Stewart Brand said in his famous Purpose statement:

"We are as gods and might as well get good at it."

In pursuit of that ideal, Whole Earth Catalog on its most basic level brought together a collection of books, equipment, tools, educational materials, techniques, and all manner of things that readers could acquire either through the WEC store or from the individual publishers and manufacturers. Every item was carefully considered, and only things with a functional purpose were included - allowing that spiritual enrichment, entertainment, and keeping a sharp mind are as practical as growing crops, learning carpentry, and making cheese. Among the many things that made the Catalog unique is that much of its content (especially as the years progressed) came from its readership. WEC actively courted suggestions and reviews from the folks who used it, bringing together a community of reader/contributors that could share their direct knowledge with their peers.

A fundamental part of the message of Whole Earth is the idea of environmentalism as opposed to conservationism. The conservationist looks to preserve what already exists, in the hope of keeping irreplaceable nature in as pristine a state as possible; the environmentalist - as espoused by Brand and his colleagues - uses appropriate technologies to have humans live with and amongst nature in a way that is better for both. Whole Earth Catalog aimed to provide, as its subtitle stated, "access to tools" for making that happen.