Can scarcity itself be the ultimate justification for value?

Of course not.

You can understand it this way: scarcity is only a "necessary condition" for value, but not a "sufficient condition." If something is merely scarce but has no use or consensus, it won't be valuable.

Take the simplest example: a stone in the park downstairs. It's unique in its texture and shape, so you could say it's "scarce," right? But is it valuable? No, it's not, because no one needs it, and it has no practical use. A painting I casually drew is also one of a kind in the world, and thus scarce, but if no one appreciates it or is willing to pay for it, it has no market value.

Therefore, for something to have value, it usually requires two things combined: scarcity + demand (or consensus/utility).

Now let's look at Bitcoin.

Its scarcity is written into its code; the total supply is 21 million. This is its foundation, ensuring it won't be infinitely over-issued and devalued like some national fiat currencies. This is the "bedrock" of its value.

But this bedrock alone isn't enough; someone still needs to build upon it. This "building" is people's demand and consensus for it. Why do people need it?

Store of Value: Some consider it "digital gold," believing it can preserve wealth during economic turmoil, much like physical gold.
Medium of Exchange: It allows for peer-to-peer transactions without banks or intermediaries, which is very convenient in certain specific scenarios.
Consensus: This is the most crucial point. More and more people believe it has value and are willing to hold and trade it. This "belief" itself creates value. Just like gold, apart from its use in jewelry and some industrial applications, isn't its greatest value derived from thousands of years of global human "consensus" on it? Everyone recognizes it, so it becomes valuable.

So the conclusion is simple: Scarcity is the "beginning" of Bitcoin's value story, but not the "end." It provides a crucial prerequisite for value creation, but what truly establishes and grows its value are the continuously added demand, application scenarios, and global consensus. If one day the whole world decides Bitcoin is useless and no one believes in it anymore, even if there's only one left, it would be worthless.