For better or worse, you know what to expect from stealth in a Bethesda game. In Skyrim you can walk into a room, steal everything from everyone present—including their clothes—and walk out without a single eyebrow being raised. If you wanted to, you could slice off each of their heads one-by-one, crouching in-between each swipe of your sword, and no-one would notice the bloody carnage taking place.

Crouching is everything in Fallout 4 too: if you crouch, you're far less likely to be spotted, and you get an indicator of how aware of your presence nearby enemies are. Enemies can see you, but they're more sensitive to movement than to what's actually there—meaning that, if you're spotted, standing still often saves you. Enemies can also hear gunfire and head in that direction, and any enemy you shoot but don't kill will investigate where the shot came from. So far, so logical… from a gameplay point of view at least.

But the enemies in Fallout 4 are also incredibly stupid, forgetful, and oblivious to their environments. In my game I have a silenced sniper rifle, and I go around shooting things in the head (Gun Nut 2 to attach suppressors to guns, Ninja perk to increase the damage bonus for surprise attacks). The enemies in Fallout 4 simply have no defence against this tactic, because they're made to deal with head-on attacks and don't notice that their mate's head has just exploded a few metres away. In fact, they happily patrol over it. They might even see you in the flesh, in the act of killing their precious commander, but if you run away and crouch then 20 seconds later it's all forgotten.

What makes this stealth system unusual is in how it scales—because, in a mechanical sense, it can't. In a stealth game like Metal Gear Solid V, you acquire better gadgets and outfits that open up new ways to attack. In Fallout 4, you crouch and use weapons in exactly the same way from start to finish. Bethesda empowers the player not by adding more options, but by abandoning any pretence that Fallout 4 is based on a physical world.

That's odd given the game's world is built on the illusion of realism. There are countless lines of NPC dialogue to be heard, choices to be made, and endless spontaneous engagements across the wasteland all designed to create a living, breathing world. Sure, Fallout 4 isn't wholly realistic, but it's a game we're expected to take seriously. And yet, as you level up the stealth system, it becomes more abstracted from what is being visually represented. Enemies become blind to your presence, walking right by you as you're crouched out in the open. As the game progresses, enemies come to resemble dumb AI rather than living creatures—crude sets of rules to be easily understood and toyed with.

A method in the madness?

It's all too easy to point out tensions in AAA game design—such as every enemy in the game getting progressively blinder—without appreciating that those who made the game are likely well aware of them. The way Fallout 4's stealth operates may seem like madness at times, but there's also a method to it.

Stealth ability is improved by choosing the right perks, among which is Stealth itself. At each level it applies a percentage decrease to your chances of being spotted alongside other buffs. At level 4, you don't even need to crouch anymore. The effect is that enemies mostly stop spotting you—and even when they do, you have the capacity to escape Houdini-like from almost any situation simply by crouching. Add to this the various buffs you can apply to a sneak attack, and most enemies will go down in one shot while their friends look on like nothing's wrong. By the end of the stealth path, you can basically walk amongst the masses, casually eviscerating whomever takes your fancy. No-one bats an eyelid.

This is so bad it's brilliant. It makes absolutely no sense that Fallout 4's enemies react in the way they do—but at the same time it's enormous fun to use as a player. The game is no longer merely about finishing quests or killing things, instead the goal evolves into getting close to enemy groups and messing with them, observing what they do, and trying out lunatic strategies.

Effectively, this makes stealth a kind of developer-sanctioned god mode—something so deliberately overpowered that it wasn't reworked or removed because it's just so much fun. I focused on silenced guns for stealth in my play through, but then I saw this GIF posted by Reddit user CyborgWalrus, which shows a stealth melee build with the "Blitz" perk that lets you teleport directly to enemies in VATs. I've never looked at my sniper rifle in quite the same way since.

Of course, this enormous leap in power is also a huge fracture in the system itself: a low-level stealth character is terrible simply because the various passive bonuses aren't active, whereas the high-level character is incredible.

There are other problems with stealth in Fallout 4's world. The overheard dialogue has a few gems, but it's mostly generic filler. There's the fact that the stealth systems are analogue—so your movement speed and sound are always crucial—but the on-screen feedback is rudimentary. At lower levels it's annoying how improved the enemies' senses become during a [CAUTION] phase, although that could be taken as another videogame-y touch. And though it's not a fair comparison, MGSV's guards are more interesting to observe than those in Fallout 4, which matters enormously when you spend hours scoping them out.

While MGSV offers a much more satisfying stealth experience, it has the benefit of being a uniformly-hostile open world. Stealth is everything to MGSV, but in Fallout 4 it is a small part of a much larger system. This is why Fallout 4's stealth remains, despite improvements, so mechanically basic. Light is a key part of enemy vision, for example, but you can't shoot out light bulbs. You have no means of distracting guards. The idea of actually sneaking past a group of enemies, rather than sneaking to make them explode, never really gets a look-in.

All of these characteristics, and the stark [HIDDEN] icon, bring to mind where this kind of stealth logic began. 1997's Thief by Looking Glass Software was the first FPS to make stealth the core mechanic, and many of its ideas survive intact. The idea that crouching doesn't just make you invisible in the right light but also makes enemies forget they ever saw you is perhaps Thief's most lasting mechanic.

If Thief is the mechanical root for Fallout 4's stealth system, the series' own past dictates how it works. The 2D Fallout games made non-combat specialisations viable builds, a characteristic that the more combat-heavy Fallout 3 and Fallout 4 have had difficulty representing. The stealth system in Fallout 4 is essentially this combination of the two—the nuts and bolts are classically-signposted FPS stealth mechanics, but their actual utility depends entirely on background stats.

It would be easy to say the sheer silliness of it all breaks the immersion, but this is a narrow view of what immersion in a videogame is. The gameness of a world, all those UI elements like a score or a life bar, and explicit systems can be powerful elements of immersion themselves. You can sacrifice narrative and visual logic with abandon, and many AAA games do, but as long as what the player's doing is enjoyable then they're not necessarily drawn out of that world.

What it comes down to is a weakness in our critical vocabulary about games—a grey zone around a system that's both a mash-up with easily-identified failings and capable of delivering surreal genius on a regular basis. Something like this can't be labelled good, bad, or even lazy. It feels more organic than that. It's the kind of thing that no one designer would ever have come up with, but different teams, over different games, have created through accumulation and accretion.

I don't know what to call Bethesda's take on stealth: lunatic, stupid, brilliant, amazing, surreal, frustrating, nonsensical, irresistible. The rudimentary parts drive me crazy, but when you end up as a cross between Rambo and the Invisible Man it completely changes the game—it almost feels like a cheat code. Fallout 4's stealth is a huge mess that's both wrong and irresistible at the same time. Even when you're the beneficiary, it's hard to tell whether you're laughing at it or with it.

Rich Stanton is a videogame journalist who has written for Eurogamer, Vice, The Guardian, and others. His first book, A Brief History of Videogames, was released this year. You can find him on Twitter at @richstanton.