The movement of thoughts in a man originates from four causes.  Firstly, from the natural will of the flesh; secondly, from the imagination of the world's sensory objects which a man hears and sees; thirdly from mental predispositions and from the aberration of the soul; and fourthly, from the assaults of the demons who wage war with us in all the passions through the causes which we have already mentioned. 
(St. Isaac the Syrian, Homily 3)

It would take weeks to unpack this saying of St. Isaac, and that is only to the level of my understanding.  I'm sure there are depths of meaning here that I have yet to experience and which I will never experience due to my lack of stillness.  But for now I would like to briefly explain how I understand these four sources of thoughts, or as the later Greek fathers call them, logismoi; then I would like to comment a little on the third source as it applies to the struggle to conquer bad habits.

By "natural will of the flesh," I think St. Isaac is referring to our bodily communication with our mind: My feet hurt, I'm thirsty, I'm aroused, I need to find a washroom.  What the body says to the mind we experience as thoughts which the rational aspect of our mind (ideally in submission to the noetic or spiritual aspect of our being) manages: Acknowledged, keep standing; acknowledged, get a drink of water; acknowledged, run away; acknowledged, wait for the intermission.  Similarly, all four sources of the "movement of thoughts," should be managed by the rational aspect of the mind in submission to the noetic aspect.  However, as we move out from the natural will of the flesh, it becomes more difficult.

The second source of thoughts comes from external stimuli: what we see, hear, smell, taste, etc.  And if I have a little control over my body, I have no control over what is outside me.  I think this is one of the reasons why men and women become monks: to cut themselves off as much as possible from the external stimuli that fills them with distracting thoughts.  Yet even in the world we have some control over what we see or don't see, hear or don't hear, eat or don't eat.  And whether we are monastic or in the world, at the end of the day, it is only God who saves us.  Only God can heal the mind and calm the thoughts.  But what I can do is choose, in whatever ways I can choose, not to provide unnecessary and unhelpful stimulus.  Sometimes I don't have a choice, but sometimes I do: what I look at, what I listen to, what I smell or touch or taste.  Experience teaches us what "sensory objects" disturb us most and which we are able, if we try, to avoid.  It seems to me that God often rescues me and grants peace to my thoughts if I first make some effort, some effort to control what I allow my eyes to see and my ears to hear.  

The third source of thoughts are our own "mental predispositions" and "aberration of the soul," and the forth is from the demons "who wage war in all the passions through the causes which we have already mentioned."  That is, the demons use all of the above in their warfare against us.  For example, I may smell a barbecue cooking somewhere (source #2), have a disgruntled disposition that is angry at God and thinks I deserve a break (source #3) and feel hungry (source #1).  These the demons use to war against my resolve not to eat between meals or to be thankful for the meal I have or whatever godly resolve that I have committed myself to.  It is that these sources of thoughts work together that often foils our resolve.  I think, "Oh, that smells good!  And I have been so good for so long, really I deserve a break--God will understand [yes, more than I know !] and I am really hungry after all...."  Perhaps others experience this inner warfare differently, but for me, the scenario that often defeats me is the coordinated attack of all the sources at once.  However, more on this another time.

What I would like to talk a little more about today are "mental predispositions" and "the aberration of the soul."  It seems that it is here that we often succumb because we figure something like this: "If I really think this, it must be what I really think."  That is, if I really experience covetous thoughts about my neighbour's wife or car or job or house, then it must mean that I really do want my neighbour's wife or car or job or house.  But I don't really want my neighbour's wife--it's taken me thirty-three years to build the relationship I have with my wife: why would I want to start all over again, or what makes me think I could do better?  I have enough headaches with my own car and house and job, someone else's will only be more stressful, not less.  I don't really want what my neighbour has (or seems to have).  So if I don't really want what my neighbor has, what is this thing in me that wants it?  Ah, that's what St. Isaac calls "the aberration of the soul," it is my mental illness, my spiritual disease.  

There are many aberrations of the soul, some we are born with, some we develop as mental predispositions: same sex attraction, kleptomania, gluttony, pedophilia, a driving desire to win, to be the best, to be right, to control.  All of these (and hundreds more) can come from some combination of inherited or learned aberration of the soul or mental predisposition.  They are not who we really are even though we really, really feel them.  These aberrations of the soul are manifestations of our sickness; it is who we were, not who we are becoming.  St. Paul gives a list in 1 Corinthians chapter six of what the Corinthian Christians were: fornicators, idolaters, adulterers, homosexuals, sodomites, thieves, covetous, drunkards,  revilers, extortioners.  These (and more) are what all of us in the aberration of our souls and in our mental predispositions have been or would be if given the opportunity.  It is sinners such as these, sinners such as I, whom God saves.  However, salvation is not merely the forgiveness of sins, it is also the transformation of the life, it is nothing less than transfiguration with Christ, it is the becoming of who we are in Christ.

But how does this transformation take place?  St. John tells us in 1 John 3: 2, 3 the following: "Beloved, now we are children of God; and it has not yet been revealed what we shall be, but we know that when He is revealed, we shall be like Him, for we shall see Him as He is.  And everyone who has this hope in him purifies himself, just as He is pure."  Who we are becoming is not yet seen--even though we are children of God already.  However, transformation takes place in seeing Him.  Even now, before the end, in prayer and quietness of heart we visit the end, we catch a glimpse of the eschaton, and in some small way we see Him--and in seeing Him in some small way, be become like him in some small way.  In fact, St. John tells us, that even the hope of seeing him works purity in us, and by purity I mean healing of the soul.

Of course we have to want it, or want to want it.  And just as it is with anything we want, we must begin to work at it.  Not that we can change ourselves, we cannot; but we can reach out for what only God can give us.  We can begin to act the way we want to be.  We can begin to cut off what feeds and strengthens what we were.  We can have this hope in us, this hope that in seeing Him, we will become like Him.  And most of all, when the thoughts from the aberrations of our soul, the thoughts of the Old Man, the thoughts coming from our sickness seem to overpower us as our thoughts, we must relax (that's right, relax), remind ourselves that it is our sickness speaking to us, and turn gently in our hearts and mind to the One who heals the sick, to the great physician.  And, perhaps, if we do this often enough we may catch a glimps in some small way of the Physician Himself and in glimpsing in some small way experience transformation in some small way.