In Parshas Shemini, we read that an earthenware vessel (“keli cheres”) has special halachos regarding tumah and taharah (purity and impurity): “And any keli cheres into which they (impure animal carcasses) fall shall contaminate all that is therein, and you must break it.” (Vayikra 11:33)
 
Chazal explain that, unlike vessels of other materials, which transmit tumah via physical contact, earthenware vessels transmit tumah only via entry to their inner airspace. Touching a keli cheres on its surface does not per se cause transmission of tumah; one must enter the keli, but need not touch it, in order for tumah to be conferred.  
 
Furthermore, unlike kelim of other materials, a keli cheres cannot be rendered tahor (pure) by immersion in a mikveh or mayan (spring). The only solution for a keli cheres which is tamei (impure) is to break it (which halachically includes physically and permanently rendering it unfit for its current use). (See Rashi ibid., from Toras Kohanim and Gemara Chullin.)
 
What is it about a keli cheres that precipitates such unusual halachos?
 
Chazal tell us that earthenware cannot be kashered, as it never fully expels that which it absorbs, unlike metal, which expels all absorbed taste when kashered. This physical/halachic quality of earthenware may shed light upon a spiritual quality or message, reflected by the distinctions between the regulations of tumah and taharah of earthenware and other materials.
 
Adverse and corrupt ideas and influences typically come in two forms. One is discernable and substantive, such that the deleterious aspects of the idea or influence are readily perceived and able to be grasped and addressed. The other is elusive, such that it is certain that evil and corruption are present, yet they cannot be pinpointed, quantified or definitely and securely extricated.
 
The former of the above two manifestations of evil is represented by the tumah of normative vessels, such as those made from metal. These vessels take in yet fully expunge non-kosher absorption, and they transmit tumah via contact with any part of them. Non-kosher absorption and tumah can be fully removed from these vessels without question. These vessels’ character is that of clarity and definitiveness, and they are thus dealt with in a normative fashion.
 
On the other hand, the non-kosher and tumah/taharah qualities of an earthenware vessel reflect lack of clarity, quantification and control. Even after undergoing kashering, a keli cheres still has residual non-kosher absorption. The problem with cheres is not the tumah or non-kosher content per se; rather, the obfuscation of the keli cheres itself regarding its negatives, and the inability to rid it of impure and non-kosher elements, dictate that the only solution is destruction, for one cannot deal with such a keli in a normal fashion. Although one may subject a keli cheres to kashering, the absorption is ever present, for such is the nature of the vessel. This elusive character is manifest by the fact that the earthenware vessel conveys tumah only upon entrance into it, for it is the very environment of the vessel, which traps and does not fully release, which confuses and cannot provide clarity, that poses the threat.

In the case of normative vessels, one purges the keli from tumah or non-kosher absorption and leaves the object intact, as the tumah or non-kosher absorption can be easily removed, and the vessel is not an impediment for such. On the other hand, when dealing with cheres, the keli itself must be eradicated from its present state of existence.

The tumah/taharah and kashrus regulations of normative vessels reflect negative influences and ideas which can be discerned and quantified and purged. Although evil is present, one can recognize and deal with it. However, the tumah/taharah and kashrus regulations of earthenware depict the negative and evil which must be avoided and condemned from afar, with total destruction of the entirety as the only real solution. Even if no specific adverse elements are overtly detectable, the nature of the situation fosters evil and masks it, such that the evil cannot be purged or effectively addressed.

We often confront ideas which are blatantly antithetical to Torah values. These ideas are easily categorized as such, and those who harbor them can at times be logically persuaded to renounce their erroneous philosophies. Even absent such renunciation, one can readily recognize the undesirable ideas or qualities and deal with them. On the other hand, we are at times unknowingly or unexpectedly accosted by those who proffer "nuanced" or "more complex" notions regarding emunah (faith) and halachic parameters, or regarding issues of right and wrong in terms of interpersonal matters. Deep down, we know that something is very wrong, but we cannot quantify it, all the while the individuals who profess these notions articulate seemingly contradictory and unclear messages which confuse and obfuscate, leading to no clear path.

This latter category is the manifestation of tumas keli cheres, and we must avoid engagement therewith and dismiss its validity.

In presenting the halachos of tumah and taharah, Parshas Shemini provides guidance for confronting adverse influences and ideas. Let us mimic the keli mateches (metal vessel), which reflects clarity and perceptibility, and purge ourselves of any negative traits and beliefs, arriving fully intact at ultimate levels of self-improvement and taharah.