Both sense data and geometric proofs are flawed ways of gaining knowlege

The argument

The question of where knowledge comes from has classically been answered in two ways. Empiricism grounds knowledge in sense data, in what observation and experiment deliver to us, while rationalism grounds it in reason, in the manner of geometric proofs derived from premises the mind is said to hold innately. Proponents of this argument hold that neither route survives examination, and that the failure of both is what makes knowledge impossible rather than merely difficult. The empirical route fails, on this view, in two ways at once. The scientific method contains bias: the observer selects what to observe, and that selection is not itself delivered by observation. It also proceeds by reduction, breaking complex systems into smaller parts for study, and those parts are insufficient to explain the system they were taken from. What is gained in tractability is lost in fidelity, so the resulting picture is never a picture of the whole thing. The rationalist route fails differently. It rests its entire edifice on innate knowledge, on starting points the mind is assumed to possess. But an assumption is precisely what has not been verified, and a proof is only as secure as what it proceeds from. A flawless chain of reasoning from an unverified premise yields no certainty at the end of it. Because these two routes exhaust the available options and each is fundamentally flawed, proponents conclude that certain knowledge is not attainable. The practical consequence they draw is skepticism, not as a rival source of knowledge but as the appropriate posture given the limits just described. The skeptic remains an inquirer, still looking for the truth and never satisfied that it has been reached. On this account that permanent dissatisfaction is the most honest position available within human constraints.

Premises

Counter-arguments

There are truths that are not deniable. They can be addressed through inferential rules. If there are two chairs in the room, there are two chairs in the room. If one has the experience with the content that there is something green in front of him, then there is something green in front of him. By observation and reason, humans can gain knowledge and undeniable truth.

Rejecting the premises

[Rejecting P1] Bias and reduction are limitations of a method in practice, not demonstrations that it yields nothing. A great deal of scientific practice consists of corrections for bias — controls, blinding, replication, pre-registration, peer review — and reduction is a strategy rather than a commitment, since many sciences work with emergent and system-level explanations. [Rejecting P2] The characterisation is a caricature. Rationalist positions do not generally rest on unverified innate knowledge; the standard cases are logic and mathematics, whose claims are established by proof. The argument itself relies on inference throughout, so if the rational route delivers nothing, this argument delivers nothing either. [Rejecting P3] The conclusion is self-defeating twice over. It is advanced as something known, and it moves from "neither method delivers certainty" to "knowledge is impossible", which holds only if knowledge requires certainty — a demanding standard the premise never defends and which most accounts of knowledge reject. The position's own recommendation of skepticism as the best way to gain knowledge concedes the point, and the counter supplies the ordinary cases: that there are two chairs in the room is something one can simply know.