As we have seen, the Mishna (2a) lists four basic types of nezek for which a person will be required to pay restitution. The Gemara on daf 4b quotes baraitot that expand the number of types of nezek by including examples that fit into the broader categories presented by the Mishna. Rabbi Oshaya enumerates 13 types of avot nezikin (including, for example, people who borrow objects or are given things to watch and then do not return them or allow them to get lost or stolen); Rabbi Hiyya finds 24 avot nezikin (including, for example, robbers and thieves).
Another category included by Rabbi Ḥiyya is examples of hezek she-eno nikkar – damage that was done that cannot be seen. The examples are cases where someone made someone else’s tithes tameh or mixes tithes in with regular produce, or libates his wine to an idol. In all of these situations, although there is no apparent change in the object itself, it no longer can be used and therefore has no value. In such cases, if the person did the damage on purpose he will be held responsible, but if it was accidental he will not have to pay.
In fact, the Gemara in Massekhet Gittin (daf 53) brings a disagreement as to whether hezek she-eno nikkar is considered damage. Ḥizḳiyya believes that hezek she-eno nikkar shemah hezek – that invisible damage is considered to be damage and the person who does such damage should always be held responsible. It is the sages who freed the person doing the damage by accident from paying, since they wanted to encourage him to admit what he did. Rabbi Yohanan disagrees, arguing that hezek she-eno nikkar lo shemei hezek – invisible damage really cannot be considered to be damage, yet the sages obligated someone who did the damage on purpose to pay in order to keep people from doing damage to one another.
Reacting to Rabbi Yohanan’s position, the Ḥatam Sofer asks how the Torah could possibly ignore significant financial damage done by one person to another. While admitting that the cases of damages discussed in the Torah are always situations of physical damage, he suggests that cases like these were left by the Torah to the Sages for them to rule according to societal needs. In the Shiṭṭa Meḳubbeẓet the point is made that it is clearly forbidden to do hezek she-eno nikkar for reasons of ve-ahavtah le-rei’ahah kamokhah (Vayikra 19:18) or ve-hai ahikah imakh (Vayikra 25:36); the discussion in our Gemara deals solely with monetary restitution and the possibility that cases where there is no physical damage with require no compensation.