Gaslighting is a form of psychological abuse in which false information is presented with the intent of making a victim doubt his or her own memory and perception. It may simply be the denial by an abuser that previous abusive incidents ever occurred, or it could be the staging of bizarre events by the abuser with the intention of disorienting the victim.
Some times gaslighting is an end in and of itself; the abuser enjoys being able to dictate reality for the victim.... Or, and this is probably way more common, gaslighters are trying to manipulate people for their own ends... the victim feels that their feelings and perceptions are “wrong”—so wrong that the gaslighter basically implies that the person should stop trying and let the gaslighter tell them what to think and feel.
This is exactly what Walt is doing with Jesse and Skyler. But Skyler is about twenty years older than Jesse and she ain't having it. Jesse is more inclined to self-blame, so he is easily manipulated. It's ironic that Gilligan has gone for a deepening of Walt and Jesse's relationship, which I wanted to see from the start of Season 1, but he has done it by making it into abuse.
In her excellent review of the latest episode frenchani says:
Cranston is so good that you can see that sometimes Walter is meaning what he says and consciously manipulating the others at the same time, mixing genuine feelings, accurate facts and actual calculation. It's both impressive and heartbreaking, especially when he's pushing Jesse's buttons.
frenchani also talks about the use of poison and pests as metaphors throughout the episode - the use of poison to drive out the pestilent thing. And two TV films - both showing machine guns - once as tragedy once as Three Stooges. Three Amigos. Harkback to Fly. And in general the layering and symbolism in this episode was so intense it's amazing it can move for the weight of significators. And yet it does move so lightly along.