user10762: I've heard it said that meditation is not a linear path and that every time you sit is like the first time but that you get better at sitting for the first time.  If this is the case and you don't actually make gains in a linear way then can it also be said that if you stop doing it that you will not go backwards or lose what you have learnt because you didn't go anywhere to begin with? 

user8044: Meditation is not linear, as it involves the whole of ourselves. There is one part/side of us that is connected to our rationality, logic, linear thinking, and understanding. The other side of us is connected to feelings, nurturing, caring, compassion, love, and all the emotional qualities. This is how our right and left hemisphere in the brain is programed. The left side of the brain processes information in a linear manner. It processes from part to whole. It takes pieces, lines them up, and arranges them in a logical order; then it draws conclusions. The right brain however, processes from whole to parts, holistically.
Intellectual understanding about meditation is never the same as the actual experience of it.  It is similar to that of having to bite into a mango to know its taste. We can read everything that there is about a mango – that it can be sweet, delicious, soft, etc. but we cannot imagine its taste unless we get the feeling of the mango on our tongue and have the personal experience. Then we can no longer debate whether the mango is sweet or not, because we have experienced the truth. This is the difference between just thinking or thinking coupled with the experience of feeling. 
Once the meditator goes beyond the second Jhana level, the internal thinking comes to a stop, and memory of past experiences never come up.  From there on there is no such thing as a linear process.  From there on it is total awareness in staying with the breath. This is being one with your meditation.   This is ekaggata, as in ekaggatarammana, oneness of preoccupation, or singleness of preoccupation; and ekaggatacitta, singleness of mind. This kind of oneness applies to all levels of jhana. It means being focused on one thing, like the breath. You stay steadily focused on it, at the same time making it the one thing filling your range of awareness.  

user3693: While your question appears rational, I will argue that it is not and conclude with an answer to the spirit of your question based on canonical sources.  Your question is presented in two clauses.  Therefore:
First, I believe it is critical to suffer through a deconstruction of your reasoning.  Second, as meditation is ill-defined here, this answer will presume the broadest non-technique specific definition inclusive of samatha and vipassana.  Third, as I believe you have been exposed to a teaching out of context, I will attempt to rein in the exuberance of composition present in your question with some doctrine.

I've heard it said that meditation is not a linear path and that every
  time you sit is like the first time but that you get better at sitting
  for the first time.

What you have heard is not unreasonable.  It is a teaching that desperately needs context.  Linearity is a rational property (relationship or function) that represents directional succession of measurable intervals.  Linearity is a concept present in math, art, science, logic, and music.  In the broadest sense, for linearity to be rational, there must exist one of two conditions: 1) an origin and a destination or 2) an origin and a directional vector.  In order for linearity to be captured or shared in any meaningful or actionable way, there must be rational measurement.
Briefly, as to origin, it is generally safe to presume for argumentation in this context that the origin is the you of now.  But this is not as trivial as it may appear.  Because the you of now is not the same you of the now just a moment ago when you began this paragraph.  "Is this you of the now more or less informed than a hypothetical you at another now?"  Put another way, "How are the things unknown to you different now than at any other moment?"  Or in the form of a koan, "What do I not know?"  You are not static and thus neither is you as an origin.  The now shatters the illusory origin and makes both destinations and vectors equally fantastic.  All we have is now.
There is also the notion that linearity is singular; that is, it cannot represent multiple measurements or states simultaneously.  And briefly stipulating to quantum mechanics, it is certainly possible to argue the possibility of infinite, omni-directional linearity, but then if one has reached such a conclusion, such infinite linearity, when aggregated to now, is self-canceling; such that, linearity is again moot.

If this is the case and you don't actually make gains in a linear way
  then can it also be said that if you stop doing it that you will not
  go backwards or lose what you have learnt because you didn't go
  anywhere to begin with?

As to gains, your premise begins with a fallacy -- that, "gains" (or progress, development, cultivation) are dependent on linearity.  This premise does not withstand scrutiny because it presumes to the singular; that gains are not gains if they are do not fall within a specific succession of measurable intervals.
Additionally, in this context forward and backward are value judgments.  If we suspend judgment then "backwards" simply indicates gain of a different sort, which is entirely possible.  However, it can not be substantiated that lack of effort results in regression (negative gains) simply because gains are correlated to effort.  It is far more reasonable to assert that effort results in gain and non-effort results in non-gain.

While interesting for some, I respect this may be a bit mind-numbing for others. So what does this mean in a more doctrinal sense?
The first time we sit, everything is new and we are confronted by the unknown.  As we sit, we cultivate.  What is cultivation?  Cultivation is at the heart of "right effort" (Samma Vayama) and "right concentration" (Samma Samadhi).

We begin not knowing what we do not know (the unrisen).  In our
  sitting, something unknown (unrisen) may become known to us (arise
  within).  This may be something as simple as a whisp in the wind of
  the passing monkey mind activity.  Or it may be as complex as the
  (re)introduction to sense experience.  Or it may be something entirely
  personal or unique to that particular place in time.  Once arisen, we
  gain awareness.  With awareness, we have less claim to the mental
  fermentation associated with ignorance and are charged to be heedful.

(MN 2 Sabbasava Sutta)

Our right effort suggests four great endevours: 1) to prevent the
  arising of unarisen unwholesome states; 2) to abandon unwholesome
  states that have already arisen; 3) to arouse wholesome states that
  have not yet arisen; 4) to maintain and perfect wholesome states
  already arisen.

(DN33,AN4.13)

"The Buddha recommended the four supreme efforts as skillful means. 
  They are called 'supreme' because they are supremely difficult and
  supremely beneficial."

"Being Nobody, Going Nowhere: The Foundation of Buddhist Thought", Volume 3, By Geshe Tashi Tsering, Ayya Khema

"For a disciple who has conviction in the Teacher's message & lives to
  penetrate it, what accords with the Dhamma is this: 'Gladly would I
  let the flesh & blood in my body dry up, leaving just the skin,
  tendons, & bones, but if I have not attained what can be reached
  through human firmness, human persistence, human striving, there will
  be no relaxing my persistence.'"

MN 70 Kitagiri Sutta

Our right concentration suggests exertion activates five mental
  factors.  Stated in their usual order the five are: initial
  application of mind (vitakka), sustained application of mind (vicara),
  rapture (piti), happiness (sukha), and one-pointedness (ekaggata). 
  When concentration is cultivated, these five factors arise and
  counteract the five hindrances.  Each mental factor factor opposes a
  particular hindrance.  1) Initial application of mind, through its
  work of lifting the mind up, counters dullness and drowsiness.  2)
  Sustained application, by anchoring the mind, drives away doubt.  3)
  Rapture denies ill will, 4) happiness excludes restlessness and worry,
  and 5) one-pointedness counters sensual desire, which may arguably be
  the most alluring inducement to distraction.  Thus, with the
  strengthening of the absorption factors, the hindrances fade out and
  subside.

The Path of Purification, Visuddhimagga 88-109
So, in conclusion, speaking to the spirit of your question:
Cultivation and practice is both sufficient and necessary to (using your word) "make gains".  Lack of effort may be a sufficient condition for unrisen unwholesomeness, but it is not a necessary condition.  Can one lose or forget what one has learned?  Certainly.  But one may just as easily forget to apply/practice what one has learned without losing the learning.
If one is judging outcomes, meditate on the difference between not knowledge and practice.

10762: <p>I've heard it said that meditation is not a linear path and that every time you sit is like the first time but that you get better at sitting for the first time.  If this is the case and you don't actually make gains in a linear way then can it also be said that if you stop doing it that you will not go backwards or lose what you have learnt because you didn't go anywhere to begin with? </p>
 8044: <p>Meditation is not linear, as it involves the whole of ourselves. There is one part/side of us that is connected to our rationality, logic, linear thinking, and understanding. The other side of us is connected to feelings, nurturing, caring, compassion, love, and all the emotional qualities. This is how our right and left hemisphere in the brain is programed. The left side of the brain processes information in a linear manner. It processes from part to whole. It takes pieces, lines them up, and arranges them in a logical order; then it draws conclusions. The right brain however, processes from whole to parts, holistically.</p>

<p>Intellectual understanding about meditation is never the same as the actual experience of it.  It is similar to that of having to bite into a mango to know its taste. We can read everything that there is about a mango – that it can be sweet, delicious, soft, etc. but we cannot imagine its taste unless we get the feeling of the mango on our tongue and have the personal experience. Then we can no longer debate whether the mango is sweet or not, because we have experienced the truth. This is the difference between just thinking or thinking coupled with the experience of feeling. </p>

<p>Once the meditator goes beyond the second Jhana level, the internal thinking comes to a stop, and memory of past experiences never come up.  From there on there is no such thing as a linear process.  From there on it is total awareness in staying with the breath. This is being one with your meditation.   This is ekaggata, as in ekaggatarammana, oneness of preoccupation, or singleness of preoccupation; and ekaggatacitta, singleness of mind. This kind of oneness applies to all levels of jhana. It means being focused on one thing, like the breath. You stay steadily focused on it, at the same time making it the one thing filling your range of awareness.  </p>
 3693: <p>While your question appears rational, I will argue that it is not and conclude with an answer to the spirit of your question based on canonical sources.  Your question is presented in two clauses.  Therefore:</p>

<p><strong>First</strong>, I believe it is critical to suffer through a deconstruction of your reasoning.  <strong>Second</strong>, as meditation is ill-defined here, this answer will presume the broadest non-technique specific definition inclusive of <em>samatha</em> and <em>vipassana</em>.  <strong>Third</strong>, as I believe you have been exposed to a teaching out of context, I will attempt to rein in the exuberance of composition present in your question with some doctrine.</p>

<blockquote>
  <p>I've heard it said that meditation is not a linear path and that every
  time you sit is like the first time but that you get better at sitting
  for the first time.</p>
</blockquote>

<p><strong>What you have heard is not unreasonable.</strong>  It is a teaching that desperately needs context.  Linearity is a rational property (relationship or function) that represents directional succession of measurable intervals.  Linearity is a concept present in math, art, science, logic, and music.  In the broadest sense, for linearity to be rational, there must exist one of two conditions: 1) an <strong>origin</strong> and a destination or 2) an <strong>origin</strong> and a directional vector.  In order for linearity to be captured or shared in any meaningful or actionable way, there must be rational measurement.</p>

<p>Briefly, <em>as to origin</em>, it is generally safe to presume for argumentation in this context that the origin is the you of now.  But this is not as trivial as it may appear.  Because the you of now is not the same you of the now just a moment ago when you began this paragraph.  "Is this you of the now more or less informed than a hypothetical you at another now?"  Put another way, "How are the things unknown to you different now than at any other moment?"  Or in the form of a koan, "What do I not know?"  You are not static and thus neither is you as an origin.  The now shatters the illusory origin and makes both destinations and vectors equally fantastic.  All we have is now.</p>

<p>There is also the notion that linearity is singular; that is, it cannot represent multiple measurements or states simultaneously.  And briefly stipulating to quantum mechanics, it is certainly possible to argue the possibility of infinite, omni-directional linearity, but then if one has reached such a conclusion, such infinite linearity, when aggregated to now, is self-canceling; such that, linearity is again moot.</p>

<blockquote>
  <p>If this is the case and you don't actually make gains in a linear way
  then can it also be said that if you stop doing it that you will not
  go backwards or lose what you have learnt because you didn't go
  anywhere to begin with?</p>
</blockquote>

<p>As to gains, your premise begins with a fallacy -- that, "gains" (or progress, development, cultivation) are dependent on linearity.  This premise does not withstand scrutiny because it presumes to the singular; that gains are not gains if they are do not fall within a specific succession of measurable intervals.</p>

<p>Additionally, in this context forward and backward are value judgments.  If we suspend judgment then "backwards" simply indicates gain of a different sort, which is entirely possible.  However, it can not be substantiated that lack of effort results in regression (negative gains) simply because gains are correlated to effort.  It is far more reasonable to assert that effort results in gain and non-effort results in non-gain.</p>

<hr>

<p><strong>While interesting for some, I respect this may be a bit mind-numbing for others. So what does this mean in a more doctrinal sense?</strong></p>

<p>The first time we sit, everything is new and we are confronted by the unknown.  As we sit, we cultivate.  What is cultivation?  Cultivation is at the heart of "right effort" (Samma Vayama) and "right concentration" (Samma Samadhi).</p>

<blockquote>
  <p>We begin not knowing what we do not know (the unrisen).  In our
  sitting, something unknown (unrisen) may become known to us (arise
  within).  This may be something as simple as a whisp in the wind of
  the passing monkey mind activity.  Or it may be as complex as the
  (re)introduction to sense experience.  Or it may be something entirely
  personal or unique to that particular place in time.  Once arisen, we
  gain awareness.  With awareness, we have less claim to the mental
  fermentation associated with ignorance and are charged to be heedful.</p>
</blockquote>

<p>(<a href="http://www.accesstoinsight.org/tipitaka/mn/mn.002.than.html" rel="nofollow noreferrer">MN 2 Sabbasava Sutta</a>)</p>

<blockquote>
  <p>Our right effort suggests four great endevours: 1) to prevent the
  arising of unarisen unwholesome states; 2) to abandon unwholesome
  states that have already arisen; 3) to arouse wholesome states that
  have not yet arisen; 4) to maintain and perfect wholesome states
  already arisen.</p>
</blockquote>

<p>(DN33,AN4.13)</p>

<blockquote>
  <p>"The Buddha recommended the four supreme efforts as skillful means. 
  They are called 'supreme' because they are supremely difficult and
  supremely beneficial."</p>
</blockquote>

<p>"Being Nobody, Going Nowhere: The Foundation of Buddhist Thought", Volume 3, By Geshe Tashi Tsering, Ayya Khema</p>

<blockquote>
  <p>"For a disciple who has conviction in the Teacher's message &amp; lives to
  penetrate it, what accords with the Dhamma is this: 'Gladly would I
  let the flesh &amp; blood in my body dry up, leaving just the skin,
  tendons, &amp; bones, but if I have not attained what can be reached
  through human firmness, human persistence, human striving, there will
  be no relaxing my persistence.'"</p>
</blockquote>

<p><a href="http://www.accesstoinsight.org/tipitaka/mn/mn.070.than.html" rel="nofollow noreferrer">MN 70 Kitagiri Sutta</a></p>

<blockquote>
  <p>Our right concentration suggests exertion activates five mental
  factors.  Stated in their usual order the five are: initial
  application of mind (vitakka), sustained application of mind (vicara),
  rapture (piti), happiness (sukha), and one-pointedness (ekaggata). 
  When concentration is cultivated, these five factors arise and
  counteract the five hindrances.  Each mental factor factor opposes a
  particular hindrance.  1) Initial application of mind, through its
  work of lifting the mind up, counters dullness and drowsiness.  2)
  Sustained application, by anchoring the mind, drives away doubt.  3)
  Rapture denies ill will, 4) happiness excludes restlessness and worry,
  and 5) one-pointedness counters sensual desire, which may arguably be
  the most alluring inducement to distraction.  Thus, with the
  strengthening of the absorption factors, the hindrances fade out and
  subside.</p>
</blockquote>

<p><a href="http://www.accesstoinsight.org/lib/authors/nanamoli/PathofPurification2011.pdf" rel="nofollow noreferrer">The Path of Purification, Visuddhimagga 88-109</a></p>

<p>So, in conclusion, speaking to the spirit of your question:</p>

<p>Cultivation and practice is both sufficient and necessary to (using your word) "make gains".  Lack of effort may be a sufficient condition for unrisen unwholesomeness, but it is not a necessary condition.  Can one lose or forget what one has learned?  Certainly.  But one may just as easily forget to apply/practice what one has learned without losing the learning.</p>

<p>If one is judging outcomes, meditate on the difference between not knowledge and practice.</p>
