positive externality. If you want LESS of something you would increase the tax, thereby increasing the cost of producing or increasing the purchasing price for the consumer. You would do this if you thought there was overproduction of this good and less of it would be desirable for society. The good in this case creates a negative externality. With this in mind, the following two articles present an interesting case study in taxation of a specific good.
The second article "Senate Considers Federal Tax On Soda" discusses a bill, ALSO submitted in the Senate that proposes a 3 cent tax per 12 ounces on soft drinks (soda, Gatorade, energy drinks, etc). The implication is that these are not a desirable good and consumption of less of it is good for society. This tax would serve to increase the cost/price of these categories of drinks, decreasing the demand hence the quantity supplied of the good. If producers/suppliers are supplying less, then they are going to need to hire fewer workers and most likely have to lay-off workers. By our definition above, it would appear that the Senate believes there is over-production of soft drinks and less of it would be beneficial to society. (The graph looks like this)