I believe that each living organism has evolved to eat a specific type of food (like Darwin's finches).
There are herbivores, carnivores and omnivores. People are omnivores. Their digestive tracts are well adapted to foods that can be naturally obtained from various habitats: forest, grasslands, wetlands, etc. Among some of naturally available foods are other animals, fowl, eggs, fish, fruit, berries, nuts, seeds and edible parts of plants (roots, leaves and stalks).
Our digestive systems are adapted to eating both raw and cooked foods.
People are ill-adapted to eating processed foods or foods with chemical additives and preservatives, as well as foods that cannot be naturally found in the environment, as well as foods that cannot be obtained by hunting and gathering.
Early agriculture fits in this picture, although it is important to point out that neolithic foods have lesser nutritional value than paleolithic foods. Therefore, agriculturalists pay the price for a steady food supply by suffering from one or more kinds of nutritional deficiencies.
As humans actively transform their environment, they modify the sources and types of food they eat as well. The process of industrialization affected the way humans learned to obtain and process food. The ramifications of creating a multi-billion food industry are general decline in health, rise of obesity and chronic diseases.
Therefore, Paleo is the only logical and scientifically proven diet that allows humans to eat foods they evolved to eat. Paleo diet stems from our biology, not economy or ethics. So this is my philosophy/ideology on eating Paleo.