Which principles from "The Intelligent Investor" are still applicable in today's market?

Sure, no problem. When talking about Graham's book, The Intelligent Investor, it's like the "Nine Yang Manual" of the investment world. Despite being several decades old, its core principles feel even more precious in today’s era of information overload and rollercoaster markets.

From the perspective of an ordinary investment enthusiast, let me share a few principles I believe remain incredibly relevant today.

1. Think of the Market as an "Emotionally Unstable Business Partner" — Mr. Market

This is the book's most classic metaphor and exceptionally easy to grasp.

What does it mean?
Graham asks you to imagine the entire stock market as your business partner named "Mr. Market". This guy is highly capable, but has a flaw: extreme emotional instability, somewhat like bipolar disorder.
- When he's manic (Bull Market): He gets wildly excited, rushes to tell you prospects are booming, then offers an absurdly high price to buy your shares or tries to sell you his shares at sky-high prices.
- When he's depressed (Bear Market): He’s deeply pessimistic, convinced the world is ending, and desperately tries to sell you valuable assets at fire-sale prices.
How to use this now?
It’s simple: You can completely ignore him!
"Mr. Market" embodies those constantly fluctuating stock prices in your trading app and the fear-mongering or hype-filled headlines in financial news. When the market soars and everyone is bragging about their gains, be wary. Don’t get infected by Mr. Market's euphoria and overpay.
Conversely, when the market crashes amidst widespread despair, with headlines screaming "XX Company Has Fallen From Grace", that’s Mr. Market having a depressive episode—presenting you with a chance to buy quality assets cheaply.
The core principle: Exploit the market's emotions; don't be exploited by them.

2. Always Build in a "Safety Cushion" — Margin of Safety

This is the cornerstone of value investing and a safeguard protecting us from significant losses.

What does it mean?
Simply put: Pay fifty cents for something worth a dollar. The gap between the price you pay and the true value you assess is your "safety cushion".
Analogy: You drive a 10-ton truck across a bridge. Would you choose one rated exactly for 10 tons, or one rated for 30 tons? The extra 20-ton carrying capacity is your "Margin of Safety." It ensures you still cross safely even if your truck is slightly overloaded or the bridge has minor flaws.
How to use this now?
In investing, if your analysis (or a reliable analyst's report) indicates a stock’s fair value is around $20, you absolutely should not buy it at $20. Instead, patiently wait for the market to err, say when the price drops to $12 or even $10, before buying.
This achieves two things:
1. Higher Margin for Error: Even if your analysis is wrong and the company is only worth $15, buying at $10 still means a profit.
2. Greater Profit Potential: If your analysis is correct and the price rebounds to $20, your gains are substantial.
  Today, valuations of high-tech stocks and trendy concepts often lack any "margin of safety," hiding enormous risks.

3. Know Whether You’re "Investing" or "Speculating"

This question helps set the right mindset from the outset.

What does it mean?
Graham provides clear definitions:
- Investing: An operation based on thorough analysis promising safety of principal and satisfactory return. Investors buy "companies," focusing on whether the business can generate sustainable profits.
- Speculating: Gambling on short-term price fluctuations. Speculators buy "stock tickers," hoping someone will pay a higher price tomorrow or next week to take it off their hands.
How to use this now?
Before buying any stock, ask yourself:
- "If the stock exchange shut down for three years tomorrow, would I still want to hold this company's stock?"
- "Do I want to be a small partner in this company, sharing in its growth, or just make a quick profit?"
  This filters out impulsive, momentum-driven trades. In today’s market with instant trading and rapid information flow, it's way too easy to slide into the "speculating" abyss. Graham’s reminder acts like a brake pedal.

4. Operate Only Within Your "Circle of Competence"

This principle, later championed by his student Warren Buffett, became widely known.

What does it mean?
It means only investing in industries and companies you genuinely understand.
Like a master Sichuan chef whose strength is Sichuan cuisine. If he sees a sushi shop doing well and tries making sushi, he’ll likely fail—it’s outside his "circle of competence."
How to use this now?
The market is flooded with new concepts—AI, the metaverse, biotech—all sounding enticing. But if you're clueless about how these industries make money, their competitive landscape, or their technical moats, and just jump in because someone said "it's the future," that's akin to gambling.
Conversely, if you work in, say, banking, you understand that industry better than most. Or if you're a "foodie" deeply familiar with various restaurant and food brands—seeking opportunities within these well-known territories gives you a significant edge.

To Summarize

The core of Graham's wisdom isn't teaching complex codes or models to predict the market. It’s about forging a rational mindset (Mindset).

He teaches us that successful investing relies more on stable emotions and a sound mental framework than on superhuman intellect. In today’s noisy, temptation-filled market, these seemingly "old-school" principles become the most scarce and valuable assets for us ordinary people.