The mechanism
A market moves by matching orders. To push price up, buyers must consume the sell orders resting above. Those orders are a finite stock. When they are eaten, price can extend — but only until the next pocket of resting liquidity absorbs the move. Nothing about this is metaphorical. It is the literal mechanics of a matching engine.
The consequence is rhythm. Sustained movement in one direction depletes the liquidity that movement feeds on. The market then has to pause and rebuild that stock — a range, a consolidation, a "calm before the storm" — before it can expand again. Every accumulation and distribution phase you have ever seen is finitude in action: the system refueling before it can move.
Why this is not trivial
It is tempting to wave this away as obvious. But finitude is what makes price impact a real, measurable thing rather than an accident. Kyle (1985) built the foundational model of exactly this: in a market with finite depth, the size of a trade moves the price, and the relationship between order flow and price change — market depth — is the quantitative face of finitude. Amihud (2002) took it to the data and showed that illiquidity (price impact per unit of volume) is priced: assets that are harder to move command a return premium, and illiquidity varies over time in ways that predict returns.
So finitude is not just "liquidity runs out." It is the reason order flow translates into price movement at all, and the reason that translation is uneven — thin where liquidity is scarce, sticky where it is deep.
What it gives the trader
Finitude is why ranges resolve and why expansions exhaust. It tells you that a move burning through liquidity is spending a finite resource, and that the absence of a pause is itself information about how much fuel remains. It is the structural reason "the market needs to build liquidity before it can run" is not trader folklore but mechanics.
You cannot eliminate finitude. Liquidity is finite by definition. A market with infinite depth would not move at all.