1:
This fourth chapter of Tractate Avodah Zarah has two topics. The first topic, which is covered by the first seven mishnayot of the chapter, is concerned with statues of the pagan deities. The second topic, which is covered by mishnayot 8 to 12, is concerned with details concerning Yeyn Nesekh. (For a definition of Yeyn Nesekh see AZ 024, paragraph 5.)

2:
It seems that the stones that are mentioned in our mishnah are rather large ones arranged so that one stone rests upon two others thus forming a kind of pedestal from which the worshipper can reach the statue of the god. If t is forbidden for a Jew to derive any benefit from such stones according to Rabbi Yishma'el; according to the rest of the sages the prohibition is effective only when it is quite obvious that the stones 'belong' to a representation of the god.

3:
The god referred to in our mishnah is the Roman god Mercury, in Latin Mercurius. The Hebraized form of the name is 'Merkulis', and it is possible that there is here an example of lamdacism (the exchanging of the letter 'r' with the letter 'l'). In order to understand why this particular deity is singled out by our mishnah we must understand what this deity meant in the Graeco-Roman world.

4:
For the Romans Mercury was the god of eloquence, skill, robbers and merchants; he was also the messenger of the gods. However, in the Graeco-Roman world the Roman deities, although called by different names, were considered as being identical with a corresponding deity of another area, particularly the Hellenic world. Thus the Roman mercury is identified with the Greek god Hermes, who was the god of herdsmen, travellers and the arts as well as being the god of robbers, eloquence and the messenger of the gods as in the Roman world. Mercury and Hermes were also identified with the Egyptian god Thoth, who was the god of alchemy, wisdom, magic and mystery-doctrines; he was also the scribe of the gods and to him was accredited the invention of letters and numbers.

5:
The aspect of Mercury-Hermes that was most conspicuous in the Graeco-Roman world was as a 'herm'. This was a small pillar, usually of wood, the top of which was carved into a representation of the god (usually with prominent and exaggerated genitals). It was customary to set up a herm at the gateway to every house or apartment block and at every crossroads. It was customary to decorate the herm - including the ones at crossroads - in order to bring good luck or success in an enterprise. This is probably why the larger ones had a stone pedestal next to them to give the worshipper easier access to the head of the herm where he could place a wreath of flowers or some such decoration.

6:
It would be helpful for us to understand the ubiquity of the herm in the Graeco-Roman world if we could imagine the bell or knocker of every door to a modern house or apartment as being a religious symbol and that a similar symbol was to be found atop every set of traffic signals. The herm was so ubiquitous that in the Gemara [Berakhot 57b] we find that the sages even instituted a 'berakhah' to be recited when seeing a herm!

To be continued.

In AZ 046 we learned that any products created by utilizing wood from an Asherah are forbidden. Ronen Lautman writes:

Let's say that a Jew takes some branches from an Asherah to make the 'skhahkh' [thatch] for his sukkah. Obviously, he has transgressed the command not to derive benefit from idolatry, but is the sukkah kosher? Another question: Let's say that a Jew used branches from an Asherah in order to provide fuel for a heating stove. In the examples given in the mishnah (cooking and weaving) the ruling is not to use what was produced by using Asherah products. What is the ruling regarding a heater?

I respond:

The sages tell us of a concept of 'a mitzvah that derives from a transgression'. In a nutshell, we can't perform a mitzvah which involves a sin. Examples would be using a stolen prayer-book to recite one's prayers, giving charity from money that had been stolen, or reciting kiddush over wine previously used for idolatry. In all such cases there is no mitzvah to be accredited to the one who performs it.

It follows, therefore, that a sukkah thatched with branches from an Asherah cannot be kosher: it is an example of'a mitzvah that derives from a transgression'.

Regarding Ronen's second question: the same reasoning applies. It is forbidden to derive benefit from anything that comes from or is connected with an Asherah. One lights a heating stove in order to benefit from the warmth it provides; the warmth comes from the wood of the Asherah, hence it is forbidden.