This is a very interesting topic that you can analyse in this great novel. What makes it particularly interesting is the way in which, alongside the literal journey that the families undertake, the characters all undertake a more metaphorical journey as they venture towards a new understanding of themselves and of humanity as a whole.

You can easily discuss this through an analysis of the concept of "family" and how it changes as the novel progresses. Initially, the Joad family is shown to be united by blood and mutual commitment. However, the novel shows that the traditional concept of a family, not possessing a home or land to define its identity, becomes superceded by newer versions or definitions of the family. Consider the way in which the Joads and the Wilsons merge into one new, larger family that are equally committed to each other to try and ensure the groups survival. Note Steinbeck's comment about this phenomenon:

...twenty families became one family, the children were the children of all. The loss of home became one loss, and the golden time in the West was one dream.

The novel shows the Joad family journeying towards a changed attitude towards what makes a family, as migrants are forced to bond together in order to ensure their survival. This theme is demonstrated by Tom, who at the end of the novel, sees that "his" people are not just his family but really humanity as a whole.

What aspects of the journey theme can I discuss in The Grapes of Wrath?

The theme of journey completely dominates the novel, as the Joads and other families make their way west and experience great travails. This suggests an analogy with the ultimate classic journey, Homer's Odyssey. Tom lends himself well to comparison with Odysseus.

You might consider the two men's objectives in undertaking their sojourns and the kinds of trials they endure. But is Tom trying to return home like Odysseus, or create a new home?

Another way to think about journey in an American sense would be to look into other people who went west--perhaps an earlier or later era, such as the Gold Rush or even today. What does the novel say about California as a promised land?

And of course, any character's metaphysical or metaphorical journey is worth considering--what internal changes do the characters undergo? Perhaps focusing on some of the minor characters, such as the Joad children (Rose of Sharon?), could yield some unusual insights.

In one sense, the entire novel consists of journeys, and so writing about journey themes looks easier than it actually is. The main difficulty you’ll have in your essay is deciding which aspects of the journeys in the novel you’ll wish to cover.

One possibility would be focussing on the notion of physical vs. spiritual journey. You could focus on Jim Casy and see his journey, and eventual death, as parallel to the travels and sacrifice of Jesus Christ, with whom he shares initials.

Another possibility would be to focus on journey as loss. Just as much as a journey moves to a destination, it leaves something behind. For Granma and Grampa, whose connection with their land runs deep, the journey represents a loss of self; their displacement results in their death. You could address this theme in terms of bio-regionalism and eco-criticism.

What is a good thesis for an essay on themes in The Grapes of Wrath?

I would think that a thesis statement for The Grapes of Wrath would need to include something about the need for workers to unite and work together to achieve better wages and working conditions. The book moves relentlessly in that direction, as the Joads travel to California and try to make their way in a hostile environment that is dominated by rich landowners.

You may wish to read the enotes page on themes.  One of the stated themes is that of social commitment.  Another theme, that of exploitation of the common people by the distant wealthy who own the millions of acres of land in California and the banks is greatly expanded with the intercalary chapters.  So, perhaps you could demonstrate how these chapters further a theme.

It depends a lot on what theme you want to focus on. Let us remember that Steinbeck wrote this novel to partly comment upon the way that man exploits his fellow men in times of hardship and need. There is thus a very distinct social commentary in this excellent text that you could write about. An appropriate starter to your essay that would hook your reader in therefore might be:

Throughout history, man has displayed the sad propensity to exploit his fellow man in times of hardship.

This would allow you to go on and present this theme and write your essay. Good luck!

Given that one of the main themes of the novel is hope, you could link your thesis statement (and essay) to the journey the character/s went on in order to find the hope they needed to survive.

Therefore, a possible thesis statement would look something like this:

The journey for hope, in The Grapes of Wrath, led the character/s on a path which allowed them to look for a new way of living life.

Here's a topic that I think is relatively unexplored: the humor encountered and experienced during the journey. Many people think of the journey as grim, solemn, and depressing, but in fact there are a number of very funny episodes and characters in this book. Taking a close look at how they contribute to the complexity and success of the book might be a good approach.  Good luck!

In order to write an essay on the main themes of Grapes of Wrath, you need to select one set of inter-related themes as a focus. Your thesis statement, which serves as a topic sentence for the first paragraph, should focus on the theme you choose and the main point you are trying to make. For example, you could start with “Grapes of Wrath is a story based on Biblical themes, and thus the major episodes in it can be read typologically, as twentieth century retellings of various Biblical stories.”  Then you would focus the rest of your essay on biblical themes in the novel.