Natural Philosophy is a mod that aims to transform and rejuvenate how Minecraft biomes are decorated. It takes new blocks only used in a few biomes and new concepts in generation since old biomes such as forests were designed and applies them to all biomes in the game, putting variety and life into Minecraft's biomes.
Minecraft's biomes had a certain, unfinished charm when they were introduced early on in the game - even the singular grass color and wacky terrain shapes of Alpha had a dreamlike quality from their roughness and simplicity. Early on in the game's development, Minecraft terrain felt surreal and dreamlike due to its unfinished qualities.
As the game developed, more content was added. More biomes, more variety, more blocks and items. But the cracks in the design never went away, and instead of being charming and surreal as early on in the game's development, the issues with the design style have become more and more prominent over time.
To put it simply: they do not feel finished. They have, most of the time, almost the same amount of content they did in 1.0.0 in terms of decorations and style. What was once charming and surreal has, with the expansion of content, become boring and uninspired. At any time in the last decade, more work could have been put in to bring old biomes into a cohesive set of content.
Instead, a few new biomes have been added that do spice up the world, some desperately needed (oceanic biomes) and some less so; and forests' largest change was the introduction of bees.
Natural Philosophy aims to fix all of that. Take old biomes, some new ideas, and gripes about how Minecraft biomes don't make sense within limited evolutionary constraints, and make something new out of them. Take all of these inspirations and transform old biomes into - not necessarily new experiences, but at least visual delights.
Jungle biomes are transformed into a bi-layered tropical rainforest, with noise-distributed bush clusters on the coarse dirt and podzol ground. Above you soars a canopy 20-28 blocks tall, with an understory just a few meters over your head. Sometimes you hack your way through with a trusty machete, and sometimes you can gaze through small gaps in the foliage to see the sun.
Sparse jungles and swamps are no longer expanses of mostly mown grass, and instead vibrant mixtures of foliage: in sparse jungles, a mix of understory jungle trees and bamboo, in swamps a mixture of copses of water-tolerant swamp oaks among reedbeds and sheafs of wet, muddy grasses.
Atop windswept hills short, hardy grasses cling to the sides of slopes as stunted fir and pine trees huddle in copses, the wind making sure that the flourishing vegetation down below cannot reach into this last holdout. Above, denuded mountains still see boulders wedged into their sides from glaciers, sentinels among cliffs of rock.
Rivers see clay, gravel, mud, and sand in great abundance. No longer do scattered patches gird their shores like the drops from a painter's brush, instead wide swaths of the river have had sediment deposited over aeons such that a clay pit can be dug from beneath their slow-moving curves.
Natural Philosophy specifically takes biomes that have been underdeveloped by the game and makes them slightly more realistic, while moving away from a paradigm of flat, mown grass with the occasional higher tuft. Features before confined to one biome can be seen in many, and some blocks seldom-useful have been expanded to provide better scenery, such as azalea bushes across the understory of most forests.
Geophilic is a large inspiration of Natural Philosophy, but is less intensive.
Tectonic is one of the most gorgeous terrain generators for current versions.
Other inspirations come from too many biome mods to count, here and there. While Biomes o' Plenty is not recommended due to the sparseness of its biomes, if you're simply looking for more, it can't hurt to check it and Oh The Biomes We'll Go out.
Natural Philosophy does not change modded biomes and has no plans to change modded biomes at this time. This is in part due to the amount of work and customization that needs to go into a singular biome, and how most mods do not add enough decorations to sufficiently differentiate their biomes from Minecraft biomes.
Natural Philosophy also replaces many Vanilla generation objects with its own, more organized counterparts. Mods that modify things such as Vanilla's patch_taiga_grass or similar may not be supported.