scrapping it." The job security granted by tenure is necessary to recruit talented individuals into university professorships, because in many fields private industry jobs pay significantly more; as Schrecker puts it, providing professors "the kind of job security that most other workers can only dream of" counterbalances universities' inability to compete with the private sector: "Universities, after all, are not corporations and cannot provide the kinds of financial remuneration that similarly educated individuals in other fields expect.". Furthermore, Schrecker continues, because research positions require extreme specialization, they must consolidate the frequency and intensity of performance evaluations across a given career, and they cannot have the same flexibility or turnover rates as other jobs, making the tenure process a practical necessity: "A mathematician cannot teach a class on medieval Islam, nor can an art historian run an organic chemistry lab. Moreover, there is no way that the employing institution can provide the kind of retraining that would facilitate such a transformation... even the largest and most well-endowed institution lacks the resources to reevaluate and replace its medieval Islamicists and algebraic topologists every year. Tenure thus lets the academic community avoid excessive turnover while still ensuring the quality of the institution's faculty. It is structured around two assessments -- one at hiring, the other some six years later -- that are far more rigorous than those elsewhere in society and give the institution enough confidence in the ability of the successful candidates to retain them on a permanent basis." According to Skoble, tenure is essential because it protects academic freedom: not only in cases in which a scholar's politics may run counter to those of their department, institution, or funding bodies, but also and most often in cases when a scholar's work innovates in ways that challenge received wisdom in the field. While stating that it has flaws, she asserts that tenure plays a crucial role in preserving academic freedom. Skoble argues categorically and plainly against critics that say "tenure protects incompetent professors": "My argument is that when this happens, it is a malfunction of the system, not an intrinsic feature of its proper use. The way it is supposed to work is that incompetent professors do not get tenure in the first place. The rebuttal is 'but they do, therefore tenure is a bad idea.' But that is like arguing that because you ran a red light and caused a train