...this would be it. I'm not in a testing mood when it comes to guide moderation, so we'll restrict it to a modest blog/forum post. Yayz.

Introduction

Fighting Psycho Mantis in the original Metal Gear Solid is a real pain in the ass, not the least of which because he can actually read your mind, a feat that is tremendous for the PlayStation since it somehow just allows it to transcend the Turing Test altogether and just head straight into ESP. I don't try to figure out how it's possible to do these things either, but you and I both know that Kojima is an insane game designer to begin with. If he was ambitious enough, he could probably port Mad Dog McCree to the Atari 2600 without having to change anything whatsoever just because he could. But I know you're not here to try and wrap your mind around how Psycho Mantis is able to fight as he does. You just want to beat the jerk and move on with your life, which probably involves dreams of marrying Merryl. So let's just get down to business.

-Pepsiman

Step 1: Preparation

In order to even have a remote chance at success when fighting Psycho Mantis, you need to come into the fight properly equipped ahead of time. Since you're dealing with a boss that can work outside the bounds of the PlayStation and actually read your mind, you have to get some pretty heavy-duty equipment, which is why I recommend using the following real-life items.

• A tin foil hat. This should probably be a given in the first place; you're up against someone who can easily learn your inner thoughts, which may very well consist of thoughts that involve replicating certain pictures of dragons humping cars. (We all know you've seen that picture.) It's natural to be scared, so why not openly acknowledge that by going into the fight with your own tin foil hat? It has no real impact on the your success or failure at all, but at least you can fight knowing that you're being true to yourself. Acknowledgment of your fears is the first step to healing, after all.
• A wooden stake. Now you might want to say to me, "Pepsiman, Psycho Mantis isn't a vampire, is he?" To that I reply, no, or at least not in the traditional sense. But given the fact that the dude wears a gas mask and happens to be all around terrifying, he might be trying to reimagine the Dracula persona for a new age. "Okay," you might then retort, "but is the wooden stake still necessary? He's just a bad guy inside the TV."  To that, all I can say is that dude, Psycho Mantis can already use the overwhelming power of the PlayStation to read your god damned mind. What's stopping him from just outright crossing the pixelated boundary into the real world and causing actual havoc? Maybe there aren't any documented cases of him doing so yet, but you should still be prepared for the absolute worst.
• A box of Cheerios. If you're going to go up against an evil mind reader, the least you can do for your health after repeatedly giving yourself near heart attacks out of sheer terror is to eat a snack that can reduce your cholestoral. Every little bit helps.
• That Sony translator guy with the note pad. Just because Psycho Mantis can read your thoughts doesn't mean he'll be able to understand them outright. Providing him with an apathetic-looking translator will make him think a bit more highly of you, even if he still wants to kick your ass in the end. This might be even more true if the interpreted thoughts turn out to greatly displease him.
• A copy of those match stick puzzles from either Professor Layton or Hotel Dusk. Psycho Mantis deserves to be in as much mental pain as possible for having such an assholish ability and nothing does the job quite as well as those pesky match stick puzzles. They've befuddled you for an eternity and a half, so now it's his turn to start feeling the pain as well.
• Your self esteem. The reason will be detailed after this next section.
  

Step 2: The Actual Fighting

Once you've gathered all of the necessary items from the previous step, it's time to take on Psycho Mantis and... maybe win. I say maybe because when it comes to this fight, almost anything can happen. The fact that Psycho Mantis really can read your mind makes the actual specifics of the fight pretty random in nature. In fact, you could follow this entire guide to the letter and still horribly lose. In fact, you probably will, but that's not what you need to worry about in the first place. You came to this guide so you could learn how to kick Psycho Mantis' ass, regardless of how reliable these tips actually are, and I intend to help you to the best of my ability.

There are four separate methods you can employ that generally provide the best results. None of them actually rely on any of the items I just told you to bring, which is great because they're all actually the things that Psycho Mantis despises the most. When the guy gets pissed off, it just makes the fights all the harder anyway. So, rendering an entire section of my own guide useless aside, let's once again use bullet points to outline each method, simply because I'm American and therefore enjoy Cliff Notes and anything else which is absurdly straight and to the point. This guide would therefore be in PowerPoint if it were at all possible to do so here, but alas, even these technologically advanced forums have their limitations. But without further ado, let's break down each method.

• Don't fight at all. Just sit at the screen for a while and ponder the meaning of life. The more narcissitic you get in your philosophical references, the better. Eventually, Psycho Mantis should give up on the fight, concluding that he has nothing to gain personally from fighting you and will simply let you pass through unharmed. If your thoughts were predominantly Nietzsche in tone, he may also decide to go pick up a copy of Thus Spoke Zarathustra and come to learn plenty about the ubermensch.
• Input the Konami code... backwards. When in doubt, doing something that involves the Konami code usually works, right? I mean, on this very site, you get taken to the Contra page, so sure it must work with Psycho Mantis and it does. In fact, this is the method that I endorse the most, since it only meant that Psycho Mantis kicked my ass eight times out of seven. (Hooray for improper fractions!) Typically, after you input the Konami code backwards, Psycho Mantis will become befuddled as to why you do such a seemingly random thing during an important battle. That's for him to figure out using his PlayStation-powered ESP; you're just looking for a successful way out of that fight in one piece and by god, good sir, this is one of them.
• Ask Psycho Mantis for help writing that dissertation on the influence of thermonuclear weapon creation on the development of paper bags. Psycho Mantis actually finds that specific subject absolutely fascinating and he's be so flattered that you care about it, too, that he'll leave the room forever in a vain attempt to read somebody's mind that has information pertinent to your research. Bam. Done. Mission accomplished.
• Switch controller ports. This also results in Psycho Mantis being absolutely baffled and he will probably go on to wonder if Eternal Darkness' mind fucks did quite the number on your logic faculties. While this action alone isn't usually all you need to defeat Psycho Mantis, when it's used in tandem with any of the other three described above, your chances of beating the guy go up exponentially. Looks like this might have been the method Kojima wanted you to use to beat the guy, if he had any in mind.

Step 3: The Aftermath

So remember when I said you should bring your self esteem with you into this skirmish with Psycho Mantis? Hell no because you simply replied to this with a smartass "tl;dr" and moved on with your life? Great! Now I want you to put that self esteem in the nearest trash bin. The reasoning should be fairly apparent. You just fought a boss that was able to learn what consitutues your inner being, especially if he got help from that interpretor guy you brought along, too. The damage done to you as a result is probably pretty tremendous. So before society catches on to the fact that you're really a wretched human being with no redeeming qualities, it's best to just go ahead and throw out your self esteem. If you try hard enough, you can grow a new one in the garden.

Conclusion

Much like the act of looking at the back of the CD case to get a codec number, many people believe that beating Psycho Mantis requires extremely obtuse methods and an entire bottle of Tylenol to keep the impending migraines at bay. I hope that this guide has proven otherwise, that with enough logic and ingenuity, most anybody can defeat Psycho Mantis and proudly be able to recall the epic battle at a campfire with their kin decades later. I know I have and because you're all exactly like me, you should feel the same way. With that said, thanks for reading this guide. If you have additional tips or just want to provide feedback, you know how to get in touch.

Ciao,

Pepsiman