'When this is, that is.'
On what different levels can this statement be understood?
1) When A is, B is; A arising, B arises; this can be understood as explaining dependent arising: all things arise (and cease) in dependence upon causes and conditions. Results depend on causes. e.g. when there is contact there is feeling; when there is feeling there is attachment; etc (12 links explaining cyclic existence)
2) When A is not, B is not; A ceasing, B ceases. It is also the case that when there is no contact there is no feeling; when there is no feeling there is no attachment; and so forth. (12 links explaining liberation from samsara)
3) Results also act as causes. Things are conditioned and conditioning.
4) the statement applies not only to the 12 links of dependent origination but to all phenomena e.g all things and events, from one's unenlightened subjective experiences to Buddhahood, come into being due to the coming together of causes and conditions.
5) if everything is dependent it follows that everything is empty of existing independently.
6) Geshe Tashi also talks about 'A is only because B is' and gives the example of 'over here' and 'over there' which takes us to mutually dependency. It is only because I am 'over here' that saying 'over there' makes any sense. The same applies to 'I' and 'other'.