4 neutral states

Four neutral states:
1. States that are resulting effects of others states are themselves neutral: 
There are states, which are the resulting effects of prior advantageous and disadvantageous states
of the sensuous sphere, the fine material sphere, the formless sphere, or of the Supramundane.
These states are either a feeling, a perception, a mental construction, or a moment of consciousness. These effects are neither advantageous nor disadvantageous, but inherently neutral.
2. Unintentional actions (kiriya kamma) are neutral states: 
There are mental states, which neither are advantageous, nor disadvantageous, nor resultants.
These are unintentional inert actions, which does not cause any effects or kamma accumulation.
These states are neither advantageous nor disadvantageous, nor causes, nor effects, but neutral.
Example: Stepping on and killing an ant, not having seen it, nor wished to harm, is a neutral action. 
3. All forms of matter, materiality, and form are neutral states:
Mountains, trees, food, water, air, knives, weapons, and even atomic bombs are all neutral states.
It is the intention behind utilizing these dead passive things, which can be either good or bad.
4. Nibbana is undecided, indeterminate, and undeterminable:
The unconditioned element of Nibbana is a neutral state, causing nothing, and as such neither
advantageous, nor disadvantageous, nor a resulting effect of anything else (the element of Nibbana, not the state or conditions for a being to acquire enlightenment / nibbana).
(from Dhammasangani, the first of the seven books of the Abhidhamma)
==References==
*The Complete Book of Buddha's Lists -- Explained. David N. Snyder, Ph.D., 2006.
*http://www.thedhamma.com/
Category:Buddha's Lists