.

1. To define Psychological Egoism
2. To list four arguments used by psychological egoists
3. To understand which part of the argument is valid
4. to understand the flaws in each argument

Consider the following four sentences:  

1. People act on their own desires; therefore, they seek what they believe is good for themselves in some respect - namely the satisfaction of their desires.
2. People seek pleasures for themselves; therefore, they seek good for themselves, namely their pleasures.
3. For a given action, we can imagine a self-serving motive.
4. When we look closely, we can find an element of self-interest  as a motive for helping others.

Psychological Egoism defined:  The view that all people are motivated ONLY by what they believe to be good for themselves in some respect.

Now let us revisit the above statements & rewrite them so that they comply with psychological egoism:

1. People  ALWAYS act on their own desires; therefore, they ALWAYS  and ONLY seek what they believe is good for themselves in some respect - namely the satisfaction of their desires.

Critique:
There are two kinds of desires:
1.  Self-seeking desires - to get things for me  (a possession, a good grade...)
2.  Altruistic desires:  -  to promote the good of others for the sake of others
"Granted, we always act on our own desires, and in order to satisfy our desires. By definition, my acts are motivated by my desires!  It does not follow that i desire only to get things for myself.  . Nor does it follow that I care only about the self-centered indulgence of my desires"  (Mike Martin 13).

Example: If I see a baby fall head first into a shallow wading pool, will I immediately rush to pull his head out of the water without thinking of my  comfort lounging on a chair - or without thinking of how I will look like a here. Should I care if my name is on the front page of the paper for being a hero - for saving a baby in one foot of water?

2.  People ALWAYS AND ONLY seek pleasures for themselves; therefore, they seek ONLY SOMETHING good for themselves, namely their pleasures.

Critique:
Recall that if we can find only one contrary incident, then the premise of the argument is false.
Example:  At night the typical person loves to lie comfortably in bed, not to have to get up and perform an unpleasant task.       A child is throwing up in the middle of the night. The parent leaves the warm bed to tend to the disgusting smell of the vomit.   In a sense, the parent was not thinking of his own comfort when rising for a comfortable night's sleep.

Therefore, sometimes we do act selflessly to promote the good of others.

Further Criticism:
There are two sources of pleasure:
1. Obtaining things we see as good for ourselves
2.  Obtaining things we see as good for others (whom we care about for their sake).

Do you derive pleasure in helping your friends?
Sometimes that is true.
But do you ONLY help your friends to obtain that pleasure, or do you sometimes help friends for their own sake?
Pleasure may come from helping friends, we many times we don't help them just to obtain that pleasure that comes from doing a good deed.
Therefore, it is possible to be unselfish when we obtain pleasure from helping others.

3. For a given action, we can ALWAYS  imagine a self-serving motive.
If this is the case, psychological egoism is true.

Critique: 
To imagine is one thing
To be correct is another thing.

I can imagine each firefighter on 911 entered the World Trade Tower to gain fame and maybe book and movie contracts.

Dare I also imagine Mother Teresa was motivate by her desire to bring fame and recognition upon herself?

Only a scumbag cynic would imagine and believe such things.

4. When we look closely, we ALWAYS  find an element of self-interest  as a motive for helping others.

Therefore, psychological egoism is true.

Critique:

There is a difference between saying that self interest is the ONLY motive  or the PRIMARY motive, rather than an incidental motive.

CONCLUSION

"As long as we acknowledge some capacity for caring for others for their sake, psychological egoism is false" (Mike Martin).

On the other hand, many subscribe to the divine imperative, "Love your neighbor as yourself."   This tells mankind to love himself.  Therefore moral reason does take into the account the importance of loving ourselves and of self-interest. 

Be aware, however, that solid moral theory would place reasonable restrictions  on the pursuit of self-interest.  Therefore, if I needed to kill my supervisor to acquire his job, or steal money to purchase a dream home, or rape an acquaintance to acquire a high,  I would be violating other's human dignity.