Bhagavad Gita Verse 25, Chapter 18

anubandham kshayam himsaamanapekshya cha paurusham |
mohaadaarabhyate karma yattattaamasamucchyate || 25 ||
 
That which is begun in delusion, without considering its consequence, loss, harm and capability, that action is called taamasic.
 
anubandham : consequence
kshayam : loss
himsaam : harm
anapekshya : without considering
cha : and
paurusham : capability
mohaat : in delusion
aarabhyate : begun
karma : action
yat : which
tat : that
taamasam : taamasic
ucchyate : is called
 
Shri Krishna now explains the nature of a taamasic action, listing its characteristics. As an example, a lot of new college graduates start a career path just because they get a lot of money, but they do not fully learn about the impact on their health, whether there is any ethical compromising going on etc. They also do not stop to think whether they have the aptitude, capability, training and passion for their role. Whenever we begin any action without fully understanding its impacts and consequences, that action becomes taamasic.
 
On similar lines, many people invest money in new ventures without having done the due diligence on the business plan, understanding the market and so on. They do not take into account the potential loss of their investment, since they only focus on the potential game. Furthermore, they do not assess whether their new venture could harm the economic, political or natural environment. Even if they know what the harm is, they conveniently choose to overlook those facts. Such kind of action is also called taamasic action.
 
The root of taamasic action is taamasic knowledge, which creates a highly perverse sense of attachment towards certain object, person, situation or end goal, that everything else becomes inferior and worthless. The underlying connectedness or unity of things is forgotten. Even a simple thing like cutting our face when shaving is a taamasic action, which has happened because our mental noise shifted our focus and attention away from the action. Similarly, whenever we eat food that is tasty but creates negative long term health impacts, whenever we give importance to our tongue, we are committing a taamasic action.